What was in [at] the back of his mind?
彼は心の奥で何を考えていたか
What was that all about?
一体どうしたの［なっているの］（◆What was all that about?，What's this all [all this] about?，What's it all about?の...
What we want and need is education pure and simple.
我々に必要なのは純然たる教育だ
What went wrong?
何がうまくいかなかったの
What were you thinking of?
((略式))（失敗をとがめて）何を考えていたんだ
What will Mrs. Grundy say?
世間は何と言うだろう
What will you buy with the money?
そのお金で何を買うの？
What with one thing and another, I never get any work done.
なんだかんだで仕事がかたづかない
What would you like for dessert?
デザートに何を召し上がりますか
What 「the hell [on earth, the devil, in the world] are you doing?
一体何をやっているの
