Question: The ANT-8 was an experimental flying boat designed by a pioneering aircraft designer of what nationality?

Context paragraphs:
Tupolev ANT-8: The ANT-8 was an experimental flying boat designed by Tupolev.  It was designated the "MDR-2" (MDR meaning "Morskoi Dalnii Razvedchik", or Naval Long-Range Reconnaissance) by the military.

Martin M-130: The Martin M-130 was a commercial flying boat designed and built in 1935 by the Glenn L. Martin Company in Baltimore, Maryland, for Pan American Airways.  Three were built: the "China Clipper", the "Philippine Clipper" and the "Hawaii Clipper".  All three had crashed by 1945.  A similar flying boat, (the Martin 156), named "Russian Clipper", built for the Soviet Union, had a larger wing (giving it greater range) and twin fins.

Farman F.51: The Farman F.51 was a 1920s French maritime reconnaissance flying boat designed and built by Farman.  The F.51 was an unequal-span four-bay biplane flying boat with a crew of four.  It was powered by two Lorraine 8bd engines mounted in tractor configuration.  A pusher engined version was designated the Farman F.50 (even though the designation had been used before in 1919).

Hiro H4H: The Hiro H4H (or Hiro Navy Type 91 Flying Boat) was a 1930s Japanese bomber or reconnaissance monoplane flying boat designed and built by the Hiro Naval Arsenal for the Imperial Japanese Navy.

Sikorsky S-42: The Sikorsky S-42 was a commercial flying boat designed and built by Sikorsky Aircraft to meet requirements for a long-range flying boat laid out by Pan American World Airways (Pan Am) in 1931.  The innovative design included wing flaps, variable-pitch propellers, and a tail-carrying full-length hull.  The prototype first flew on 29 March 1934, and, in the period of development and test flying that followed, quickly established ten world records for payload-to-height.  The "Flying Clipper" and the "Pan Am Clipper" were other names for the S-42.

Andrei Tupolev: Andrei Nikolayevich Tupolev (Russian: Андрей Николаевич Туполев ; November 10, 1888 – December 23, 1972) was a pioneering Soviet aircraft designer.

Supermarine Sea Lion I: The Supermarine Sea Lion I was a British racing flying boat designed and built by the Supermarine Aviation Works for the 1919 Schneider Trophy at Bournemouth, England.  The later racing flying boat for the 1922 Schneider Trophy the Sea Lion II was a different design.

Supermarine Sea Lion II: The Supermarine Sea Lion II was a British racing flying boat designed and built by the Supermarine Aviation Works for the 1922 Schneider Trophy at Naples, Italy which it went on to win.  The earlier racing flying boat for the 1919 Schneider Trophy the Sea Lion I was a different design.

Chyetverikov ARK-3: The Chyetverikov ARK-3 ("ARKtichyeskii" - arctic) was an Arctic multi-role flying boat designed and built in the USSR from 1933 featuring a conventional flying boat hull, with high cantilever wings equipped with floats at mid-span.  The two engines were mounted in tractor-pusher fashion on a pylon above the fuselage.

Hughes H-4 Hercules: The Hughes H-4 Hercules (also known as the Spruce Goose; registration NX37602) is a prototype strategic airlift flying boat designed and built by the Hughes Aircraft Company.  Intended as a transatlantic flight transport for use during World War II, it was not completed in time to be used in the war.  The aircraft made only one brief flight on November 2, 1947, and the project never advanced beyond the single example produced.  Built from wood because of wartime restrictions on the use of aluminum and concerns about weight, it was nicknamed by critics the "Spruce Goose", although it was made almost entirely of birch.  The Hercules is the largest flying boat ever built, and it has the largest wingspan of any aircraft that has ever flown.  It remains in good condition and is on display at the Evergreen Aviation & Space Museum in McMinnville, Oregon, United States.

Supporting paragraphs: Tupolev ANT-8 Andrei Tupolev
Answer: Soviet