It's ten years since the scientist to discover the valuable chemical.
A. kept up
B. set out
C. took in
D. set about
网友回答
A. kept up
(答案→)B. set out
C. took in
D. set about
解析：考查词组：A. kept up维持，不低落B. set out开始，后面接to do，C. took in 欺骗，吸收，理解，D. set about开始，后面接动名词做宾语，和不定式搭配用set out，句意：自从科学家发现有价值的化学物质已经有10年了。选B。