英语-----名词 选什么答案.为什么.

英语-----名词 选什么答案.为什么.
6.This is one of the books that ---written in English .
A.have B.has been C.are D.is
7.Tom made a-----to the northwest of China last year.
A.travel B.journey C.visit D.stay
8.The singer and teacher who --- giving performance now --- known to us all.
A.is,are B.are,are C.is,is D.are,is
9.------enough for him.
A.One and a half cakes is
B.One and a half cake is
C.One cake and one half are
D.One and a half cakes are