Question

—_______ do you surf the Internet ?
—Once a month.

A．How soon

B．How old

C．How often

D．How long

Answer 1

C

根据Once a month，可知是询问频率。How soon是多久之后会发生某事；How old问年龄多大；How often 多久一次，回答频率；How long多长。所以选C。