问题补充：
I can’t tell when that house exactly, but it must be very long ago.
A. is built
B. will build
C. was built
D. has built
答案：
A. is built
B. will build
(答案→)C. was built
D. has built
解析：句意：我说不清那所房子确切地是什么时候建造的，但是肯定是很久以前。结合语境可知前文宾语从句中描述的是过去发生的动作，故用一般过去时态，选Ｃ。
