Which is the interrogative word in each of these sentences?

问题描述:

Which is the interrogative word in each of these sentences?
How old are you?
Do you speak French?
Can you tell me how old you are?
Could you tell me if you speak French?
是how old 不是how

How old are you?
疑问词how old
Do you speak French?
没有疑问词
Can you tell me how old you are?
没有疑问词
Could you tell me if you speak French?
没有疑问词