Early in the last century，yellow fever was one of the worst diseases known．Thousands of people （1） ______ of it every year．It had been suggested that the yellow fever virus is transmitted by the bite of a certain mosquito．It was （2） ______ （认为） that a （3）c ______ kind of mosquito would bite a person ill with yellow fever and then，flying elsewhere，bite （4） ______ person and（5）g ______ him the disease．To prove whether or not this was true，Dr．James Carroll，allowed （6）s ______ a mosquito to bite him after it had bitten a yellow fever patient．
He knew the bite of this mosquito might （7）c ______ his death；nevertheless，he made the （8） ______ （尝试）．
Dr．Carroll became very ill of yellow fever but finally（9） ______ （恢复）．The risk this hero took，however，helped to save the lives （10） ______ thousands of people．