It was the Japanese Americans. This is because Japan bombed Pearl Harbor in America, which made Americans suspicious of the Japanese Americans.
Hope this helped. Lmk if you still have a question or this explanation wasn't clear enough. :-)
The answer is option a, that is "The stamps were carved out pure limestone".This sentence is false because the stamps were actually made of another kind of rock such as stearite which is a magnesium-rich rock composed of mineral talc and some of them are also made of silver or calcite.
