Do you know the man ________ visited the Singapore in February—-Yes. He is Mr Li. He said it was his _______ visit to the United States.

Should I wear a suit for the concert tonight–No , you ________. It is not as serious as the one we went to last week .

Books are made __________ paper while paperis mainly made __________ wood.

The two girls are so alike that strangers find_____difficult to tell one from the other.

The conflict had developed into a stage ______ the two countries were gathering big troops on the border