You can keep all the files and documents you think it is convenient to get them.
13.I think it a great honour_______to visit your country.
14.Many people now make_________a rule to buy cards for their friends before Christmas.
15.__________is very clear to everyone that he's round and tall like a tree. 16.
17..In the United States, bus travel doesn't cost much as train travel, ? 18.
19..Someone is at the door, who is_________? 20.