—I want to know your son is.—He is ten years old.A. how muchB. how oldC. how longD. how m

问题补充：

—I want to know your son is.

—He is ten years old.

A. how much

B. how old

C. how long

D. how many

答案：

A. how much

(答案→)B. how old

C. how long

D. how many

解析：根据回答他十岁了，可知上句在问你的儿子多大了。A. how much多少，提问不可数名词的量B. how old 多大，问年龄 C. how long 多久D. how many多少，提问可数名词的量。根据句意，故选B。