问题
选择题
This river has changed its course many times. It _________ always located where it ________ at present.
A．isn’t; is
B．isn’t; will be
C．wasn’t; is
D．wasn’t; has been
答案
答案：C
考查时态。句意：这条河改道了很多次。它不是一直都在现在这个位置的。因为是过去不在，所以用wasn’t ，后者强调的是原先已经坐落的地方，故用完成时has been。