The new rule has been working effectively since it __________.
It was ___ it was raining so hard that we had to stay at home all day
.It was in the small house ___was built with stones by his father ___ he spent his childhood. A. which; that B. that ;where C, which; which D. that; which
_________ the project in time, the workers were working at weekends.
_________ many times, he finally understood it.
The chairman thought _________ necessary to invite Professor Smith to speak at the meeting.