Question

I don'd know A,how many his telephone number B,what is his telephone number C,what his telephone nu

ber is

Answer 1

C。what his telephone number is
我不知道他的电话号码是什么。

what his telephone number is是宾语从句，要用陈述语气。is要放在后面。排除B。
应当说电话号码是什么，即用what，而不能说电话号码是多少。排除A。

Answer 2

what his telephone number is .
宾语从句后跟陈述语序

Answer 3

C
这是一个宾语从句。考查语序，选C是陈述句语述。而且通常问号码用what 不用how many

Answer 4

C,what his telephone number is