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
网友回答
(答案→)A. tried out
B. found out
C. worked out
D. turned out
解析：
这题是词组辨析：try out试验 find out查明work out制定出、锻炼 turn out结果是，A符合句意：科学家试验了成千上万的药品才做出正确的决定。