我有几个英语题不太懂,请英语不错的人帮我解答一下,

我有几个英语题不太懂,请英语不错的人帮我解答一下,
1.When you are in_____to another person,you should usually say"How do you do"
2.At the age of eighteen,Newton went to the Cambridge Un______to study maths
3.Dark clouds are si____of coming rain
4.You are going back home.please give my best re____to your parents
5.He is my co____,a son of my aunt
6.It is sa____that there are a large number of dangerous fish in this river
7.Forests su_____us not only with wood but also with fresh air
8.Judy is a student of me____,who is going to be a doctor
9.After they became se_____,they still kept in touth with each other
10.His father is an official who works in the go____office
11.Another bridge over the Changjiang River has started and the Pr_____will be finished next year
12.The doctor suggested him to lose some we_____
13.The ex_____on his face suggested that he was greatly disappointed at the news