I cannot determine what is incorrect about either choice in this problem:
新完全マスター 文法 N4 1課：
れんしゅう２ aかbか いい ほうを えらんで ください。
７） A「メールと 電話と どちらを よく 使いますか。」
B「そうですねえ。（a電話ほど 使いません bメールの ほうを よく 使います）。」
The answer is ‘b’, but I don’t understand what is grammatically wrong with ‘a’, other than it doesn’t mirror the form of the question.
Any input would be appreciated!
Let's check the meaning of the question and the answer in English. A - Which do you use more often, email or the phone? B - Let me think...(a. I don't use it as often as the phone. b. I use email more often.)
The 'b' is a better answer, because 'a' is not really responding to the question. If the question is "Do you often use email?" or "Do you use email like a phone?"), the answer can be 'a'.
My opinion... 1)"which"(どちら) question (with the option A or B) should be answered clearly with the A or B. 2) "which" question is hardly answered in a negative form.