【题目】Scientists ______ thousands of chemicals before they decided on the right one in the end.
A. tried out B. found out
C. worked out D. turned out
在线课程【答案】A
【解析】
试题分析：句意：科学家们实验使用了几千种化学物质才最后做出正确的决定。A. tried out实验； B. found out查明； C. worked out解决；制定出；锻炼； D. turned out结果是；根据句意故选A。