Explanation
Use a subject question when you ask about the person or thing that does the action. In this pattern, "who" or "what" is the subject, so you do not use "do/does/did" in a normal question.
For example, "Who called you last night?" Here "Who" asks for the person, "called" is the past verb, "you" is the person who received the call, and "last night" shows the time. Japanese often says "だれが" or "何が" at the front, so the idea is similar. The important point is that English keeps the verb right after the subject word.
人や物が「何をしたか」をたずねるときは、主語の疑問文を使います。ここでは "who" や "what" が主語なので、ふつうの疑問文のように "do/does/did" は使いません。
たとえば "Who called you last night?" では、"Who" が「だれが」をたずねる語、"called" が過去の動詞、"you" が電話を受けた相手、"last night" が時を表します。日本語でも「だれが」「何が」を文の前に置くので、考え方は近いです。英語では、主語の疑問詞のすぐ後ろに動詞が来ることが大事です。
Examples
- Who is at the door? ドアのところにいるのはだれですか。
- What happened? 何が起こったのですか。
- Who called you last night? 昨夜、だれがあなたに電話しましたか。
- What makes you happy? 何があなたを幸せにしますか。
- Who can help us with this? だれがこれを手伝ってくれますか。
- What didn't work in the meeting? 会議で何がうまくいかなかったのですか。
Common Mistakes
Japanese learners often add "do/does/did" and keep the past verb, for example "Who did called you?" -> "Who called you?" In a subject question, the wh-word is already the subject, so the extra helper verb is not needed.
日本語話者は、主語が疑問詞の文でも "do/does/did" を足してしまい、さらに動詞を過去形のままにすることがあります。例: "Who did called you?" -> "Who called you?" 主語が who / what のときは、その疑問詞がすでに主語なので、補助動詞はふつう要りません。