From the passage, one can assume that the Japane¬se _______.

The purpose of the archaeologist is to dig up the past in order to study the activities of mankind. "Archaeology" is derived from Greek words meaning "ancient study", and experts in this field have already uncovered scores of buried cities and
evidence of old civilisations that tell us fascinating stories of vanished peoples and how they lived. Archaeology is also useful in more unusual ways. During World War II, the Japanese sent up balloons
with bombs, designed to be blown across the Pacific and to set fires along the West coast of the United States, Some of the balloons landed without exploding the bombs. An archaeologist examined some of the sand which had stuck to the balloons and pinpointed the Japanese area from which they were launched, which then became a target for
American bombers.