3.解析：因think of(想到)是固定搭配。

答案：of

2.解析：因by the name of＝named/called(名叫……)是固定搭配。

答案：by

Father's Day occurs on the 3rd Sunday in June.The idea for creating a day　1　children to honor their fathers began in Spokane，Washington.A woman　2　 the name of Sonora Smart Dodd thought　3　the idea for Father's Day while listening to a Mother's Day sermon　4　1909.

Having been raised　5　her father，Henry Jackson Smart，after her mother died，Sonora wanted her father to know how special he was　6　her.It was her father that made all the parental sacrifices and was，　7　the eyes of his daughter，a courageous，selfless，and loving man.Sonora's father was born in June，so she chose to hold the first Father's Day celebration　8　Spokane，Washington　9　the 19th of June,1910.

In 1924 President Calvin Coolidge announced the third Sunday in June　10　Father's Day.Roses are the Father's Day flowers.

语篇解读：本文介绍了父亲节的来历。最早是1909年由住在华盛顿斯波肯市的索罗拉·斯马特·杜德夫人最早提出设立父亲节，并于1910年在斯波肯市过第一个父亲节，1924年，美国总统加尔文·库利奇宣布每年6月的第三个星期天为父亲节。

1.解析：表示目的，“为”。

答案：for

20.-I think he is taking an active part in social work.

-I agree with you　　a way.

答案：in

19.Some people choose jobs for other reasons　　money these days.

答案：besides

18.The manager suggested an earlier date　　the meeting.

答案：for

17.Experts have been warning　　some time of the health risks caused by passive smoking.

答案：for

16.Scientists are convinced　　the positive effect of laughter　　physical and mental health.

答案：of；on

15.　　the silence of the pauses，we could hear each other's breathing and could almost hear our own heartbeats.

答案：In

14.Although　　my opinion，the old professor didn't come up with his own.

答案：against