The experiment _______ on the moon in July, 1971 proved that Galileo's theory of falling objects _______ true.
A.Was done; is
B.being done; was
C.done; is
D.having been done; Was
网友回答
C解析谓语proved的主语是the experiment，宾语为that从句，experiment后为非谓语动词短语作定语，实验被做且已经被做过了，故用过去分词done作定语。另外，宾语从句中的内容为客观事实，故用现在时。