Thomas Edison ____ already ____ a chemistry lab for himself by the time he ____ ten.A.has…built…was B.had…built…was C.would…build…was D.was…building…is
问题描述：
Thomas Edison ____ already ____ a chemistry lab for himself by the time he ____ ten.
A.has…built…was B.had…built…was C.would…build…was D.was…building…is
答
选B by the time he was ten. 是过去的过去 应用过去完成时
答
B. had…built…was
托马斯·爱迪生十岁前就给自己建了一间化学实验室~
答
B,因为从句是一个过去时,所以主语是发生在过去的过去,所以用过去完成时.
答
B. had…built…was
already决定了用完成时，而by the time决定了用过去完成时