Scientists photographed for the first time ever wild gorillas used a stick to test the depth of a pool before getting into it, according to a recent study.
A. which
B. what
C. that
D. when
网友回答
A. which
B. what
C. that
D. when
解析：考查名词性从句。以that引导的宾语从句，充当photographed的宾语。科学家近期首次发现野生大猩猩在进入水池之前先用一根木棒测量水的深度，科学家拍摄到了这些场面。