Then put in two t____ of honey.(首字母填空）

Then put in two t____ of honey.(首字母填空）
_____ sixteen to eighteen ,you will get thirty-four .
A.Put B.Then C.But D.And
Which word is not right?
He worked on the problem for two hours._____,he worked it out.
A.Finally B.Then C.But D.And
什么是序列词?