Question: Which german medium tank was developed in late 1930s to provide the close-in fire support for standard Japanese medium tanks in Second World War?
Context: The BT tanks (Russian: Быстроходный танк (БТ), "Bystrokhodny tank" , lit.  "fast moving tank" or "high-speed tank") were a series of Soviet light tanks produced in large numbers between 1932 and 1941.  They were lightly armoured, but reasonably well-armed for their time, and had the best mobility of all contemporary tanks in the world at that time.  The BT tanks were known by the nickname "Betka" from the acronym, or its diminutive "Betushka".  The successor of the BT tanks would be the famous T-34 medium tank, introduced in 1940, which would replace all of the Soviet fast tanks, infantry tanks, and medium tanks in service. Medium tank is a classification of tanks, particularly prevalent during World War II which represented a compromise between the mobility oriented light tanks and the protection and armour protection oriented heavy tanks.  The most widely produced, cost effective and successful tanks of World War II (the Soviet T-34, the American Sherman tank, the Japanese Type 97 and the German Panzer IV) were all medium tank designs, and the success of the concept would later lead to the development of later generations of medium tanks such as the Chieftain.  Many of the medium tanks lines became what are called main battle tank in most countries. The cruiser tank (also called cavalry tank or fast tank) was a British tank concept of the interwar period for tanks designed to function as modernised armoured and mechanised cavalry.  Cruiser tanks were developed after the Royal Armoured Corps were not satisfied with many of the medium tank designs of the 1930s.  The cruiser tank concept was conceived by Giffard Le Quesne Martel, who preferred many small light tanks to swarm to enemy, instead of a few expensive medium tanks.  There were two main types of cruiser tanks, "light" cruiser tanks and "heavy" cruiser tanks.  "Light" cruiser tanks were lightly armoured and relatively fast (for example, the Cruiser Mk I), while "heavy" cruiser tanks were more heavily armoured and slightly slower than "light" cruiser tanks (for example, the Cruiser Mk II). The "Panzerkampfwagen" IV (PzKpfw IV), commonly known as the Panzer IV, was a German medium tank developed in the late 1930s and used extensively during the Second World War.  Its ordnance inventory designation was Sd.Kfz.  161. The Type 2 Gun tank Ho-I (二式砲戦車 ホイ , Ni-shiki hōsensha Ho-I ) Support Tank was a derivative of the Type 97 Chi-Ha medium tanks of the Imperial Japanese Army in World War II.  Similar in concept to early variant of the German Panzer IV, it was designed as a self-propelled howitzer to provide the close-in fire support for standard Japanese medium tanks with additional firepower against enemy anti-tank fortifications. The Type 4 medium tank Chi-To (四式中戦車 チト , Yonshiki chūsensha Chi-To ) ("Imperial Year 2604 Medium Tank Model 7") was one of several medium tanks developed by the Imperial Japanese Army towards the end of World War II.  While by far the most advanced Japanese wartime tank to reach production, industrial and material shortages resulted in only six chassis being manufactured; only two of these were completed with neither seeing combat. The Medium Tank T20 was part of a series of medium tanks designed by the United States during the Second World War, to be the successor to the Medium Tank M4 "Sherman", and culminated in the M26 Pershing. The Type 5 medium tank Chi-Ri (五式中戦車 チリ , Go-shiki chusensha Chi-ri ) ("Imperial Year 2605 Medium Tank Model 9") was the ultimate medium tank developed by the Imperial Japanese Army in World War II.  Intended to be a heavier, more powerful version of Japan's sophisticated Type 4 Chi-To medium tank, in performance it was designed to surpass the US M4 Sherman medium tanks being fielded by the Allied forces.  A single prototype was incomplete when the war ended. The Type 1 medium tank Chi-He (一式中戦車 チへ , Ichi-shiki chusensha Chihe ) was an improved version of the Type 97 Chi-Ha medium tanks of the Imperial Japanese Army in World War II.  It had a more powerful main gun, engine and thicker armor.  It was the first Japanese tank to have a communication radio as standard equipment.  Production of the tank did not begin until 1943, due to the higher priority of steel allocated to the Imperial Navy for warship construction.  A total of 170 units were built.  All of the tanks produced were allocated for the defense of the Japanese home islands, against the anticipated Allied Invasion. The T2 Medium Tank was an American design that replaced three prototype medium tank designs started in the 1920s for an experiment conducted by United States Army.  The T2 tank never saw combat and left prototype stages and was not mass-produced with having only one built in the 1930 by Rock Island Arsenal.  Its legacy, however was the M2 light tank, developed into the M2 medium, and onto the M3 Lee and M4 Sherman medium tanks.
Answer: Panzer IV