is no need
The difficulty which we had _______ with the local people has now been removed·
The surface of the table ______ smooth enough.
At last,we found ourselves in a pleasant park ________trees providing shade(荫凉)and sat down to eat our picnic lunch.
.Manufacturers should have professional productivity and technical knowledge to ______ the quality of the products.
.It was in the 1990s _______ we were working together ____ we made friends with each other.