A can only guess
A(人)に(…が)わかるはずもない≪at≫
keep A guessing
((略式))(勝手に想像させて)A(人)の気をもませる,Aをじらす
let me guess
((略式))(相手の機先を制して)私が思うに
you can guess A
((略式))A(事)ぐらい言わなくてもわかるはずだ
you would never guess
((略式))(…だとは)夢にも思わないだろう≪that節≫
anybody's [anyone's] guess
((略式))まったく予想がつかないこと How long this will last is anybody's guess.どれぐらい続くかだれもわからない
at a guess
((英略式))推測では,だいたいの見当では At a guess, she may be 30.彼女はざっと踏んで30歳ってところかな
by guess (and by God)
当てずっぽうで
I'll give you three guesses.
容易にわかるだろう
Your guess is as good as mine.
((略式))さあ,私にもよくわからない(◆質問に対する答え)