Question: The Chengdu J-20 is what type of aircraft that is designed to avoid detection, and whose technology likely began in Germany during World War II?
Context: HNLMS "Abraham Crijnssen was a "Jan van Amstel"-class minesweeper of the Royal Netherlands Navy (RNN).  Built during the 1930s, she was based in the Netherlands East Indies when Japan attacked at the end of 1941.  Ordered to retreat to Australia, the ship was disguised as a tropical island to avoid detection, and was the last Dutch ship to escape from the region.  On arriving in Australia in 1942, she was commissioned into the Royal Australian Navy (RAN) as HMAS "Abraham Crijnssen and operated as an anti-submarine escort.  Although returned to RNN control in 1943, the ship remained in Australian waters for most of World War II.  After the war, "Abraham Crijnssen" operated on anti-revolution patrols in the East Indies, before returning to the Netherlands and being converted into a boom defence ship in 1956.  Removed from service in 1960, the vessel was donated to the Netherlands Sea Cadet Corps for training purposes.  In 1995, "Abraham Crijnssen" was acquired by the Dutch Navy Museum for preservation as a museum ship. The Boeing B-29 Superfortress is a four-engine propeller-driven heavy bomber designed by Boeing, which was flown primarily by the United States during World War II and the Korean War.  It was one of the largest aircraft operational during World War II and featured state of the art technology.  Including design and production, it was the single most expensive weapons project undertaken by the United States in World War II, exceeding the cost of the Manhattan Project by between $1 and 1.7 billion.  Innovations introduced included a pressurized cabin, dual-wheeled, tricycle landing gear, and an analog computer-controlled fire-control system that directed four remote machine gun turrets that could be operated by a single gunner and a fire-control officer.  A manned tail gun installation was semi-remote.  The name "Superfortress" continued the pattern Boeing started with its well-known predecessor, the B-17 Flying Fortress.  Designed for the high-altitude strategic bomber role, the B-29 also excelled in low-altitude nighttime incendiary bombing missions.  One of the B-29's final roles during World War II was carrying out the atomic bomb attacks on Hiroshima and Nagasaki. The Chengdu J-20 () is a stealth, twinjet, fifth-generation fighter aircraft developed by China's Chengdu Aerospace Corporation for the People's Liberation Army Air Force (PLAAF).  The J-20 made its maiden flight on 11 January 2011, but the plane was officially revealed on China International Aviation & Aerospace Exhibition in 2016.  In March 2017, Chinese media claimed that the aircraft has entered initial operational capability phase with limited service within Air Force. The flight-deck cruiser was a proposed type of aircraft cruiser, warships combining features of aircraft carriers and light cruisers designed by the United States Navy during the period between World War I and World War II.  Several designs were proposed for the type, but none were approved for construction.  The final design was developed just before World War II, and the entry of the United States into the war saw the project come to an end. Radar in World War II greatly influenced many important aspects of the conflict.  This revolutionary new technology of radio-based detection and tracking was used by both the Allies and Axis powers in World War II, which had evolved independently in a number of nations during the mid 1930s.  At the outbreak of war in September 1939, both Great Britain and Germany had functioning radar systems.  In Great Britain, it was called RDF, Range and Direction Finding, while in Germany the name "Funkmessgerät" (radio measuring device) was used. Werner C. von Clemm (27 September 1897 - 14 April 1989, Biddeford, Maine) was born into a German family that married into German nobility, the Nazi party and prominent American families.  His father-in-law was a Vice President of Citibank.  In 1922 he immigrated to the United States.  Prior to this he had served in the German army during World War I.  He was a representative of the German international banking firm Hardy & Co. and an employee of the Pioneer Import Corp., which imported materials from Germany and handled his cousin and Nazi diplomat, Joachim von Ribbentrop's champagne business.  Along with his twin brother, Karl he had become friends with U.S. oil man, William Rhodes Davis.  In the United States Werner became Vice President of Davis' company Davis & Co., which shipped large quantities of oil to Germany and became a propaganda strategist and financial aid of the America First Committee, which encouraged American isolationism.  In 1940 the Nazis seized large quantities of diamonds from Belgium and the Netherlands, which Werner was smuggling to the U.S.  The United States was neutral and did not declare war until December 1941.  To avoid detection he moved the diamonds through various European cities, shipped them to South America and they eventually found their way to New York City.  The operation was stumbled upon by mistake by agents of the Treasury Department when they searched a Budweiser beer box being carried by two American soldiers of German descent.  On inspection of the box they found it had a false bottom under which were one hundred letters and government bonds.  The letters detailed Werner's diamond smuggling operation.  After further investigation von Clemm was arrested on 28 January 1942 and was sentenced to two years in prison for his crime.  On his release he entered private banking.  He was also an agent of the German intelligence agency, Abwehr and was involved in espionage during World War II. The I-400"-class submarine (伊四百型潜水艦 , I-yon-hyaku-gata sensuikan ) Imperial Japanese Navy (IJN) submarines were the largest submarines of World War II and remained the largest ever built until the construction of nuclear ballistic missile submarines in the 1960s.  The IJN called this type of submarine Sentoku" type submarine (潜特型潜水艦 , Sen-Toku-gata sensuikan, "Submarine Special" ) .  The type name was shortened to Toku-gata Sensuikan (特型潜水艦 , Special Type Submarine ) .  They were submarine aircraft carriers able to carry three Aichi M6A "Seiran" aircraft underwater to their destinations.  They were designed to surface, launch their planes, then quickly dive again before they were discovered.  They also carried torpedoes for close-range combat.  They are considered the strategic predecessors to today’s ballistic submarines, especially to the Regulus missile program begun about a decade after World War II. The North China Type 19 (北支一九式拳銃) was a military sidearm produced during World War II by the Empire of Japan.  Produced in China during the final stages of World War II, the North China Type was most likely made in an effort to supply troops based in Manchuria when supply lines from Japan became disrupted by Allied submarines and bombing.  Officially approved by the Chief of the Ordnance Bureau, the Type 19 is very scarce with only eleven surviving examples known.  The pistol appears to be a redesign of the Type 14 Nambu pistol but all pertinent ordinance records lost during World War II. Stealth aircraft are designed to avoid detection using a variety of technologies that reduce reflection/emission of radar, infrared, visible light, radio-frequency (RF) spectrum, and audio, collectively known as stealth technology.  Development of stealth technology likely began in Germany during World War II, the prototyped Horten Ho 229 was designed for twin BMW 003 jet engines but finally powered by twin Junkers Jumo 004 jet engines being described as the first stealth aircraft.  Well-known modern examples of stealth of U.S. aircraft include the United States' F-117 Nighthawk (1981–2008), the B-2 Spirit, the F-22 Raptor, and the F-35 Lightning II. The Nambu pistols (南部拳銃 or 南部大型自動拳銃 , Nanbu kenjuu or Nanbu ōgata jidou-kenjuu ) were a series of semi-automatic pistols produced by the Japanese company Koishikawa Arsenal later known as the Tokyo Artillery Arsenal.  The series had five variants, the Type A Model 1902 (also called the Grandpa Nambu), the Type A Model 1902 Modified (also known as the Papa Nambu), the Type B (also known as the Baby Nambu), the Type 14 (南部十四年式自動拳銃) and the Type 94.  The pistols were designed by Kijiro Nambu and saw extensive service during the Russo-Japanese War, Second Sino-Japanese War and World War II.  The Type A was made in very small numbers.  Type A Modified and Type B Nambus were never formally adopted by any branch of the armed forces of Imperial Japan but were sold to officers through officer stores.  The Type 14 was adopted as an official sidearm.  As World War II progressed, and particularly in the final year of the war, in order to speed production, Type 14s began to be more hastily manufactured with a subsequent decline in quality.
Answer: Stealth aircraft