Knowing _____, as a matter of fact, one shouldn’t know is a terrible thing

Why haven’t you asked her to comehere—She _______ an important experiment when Ifound her and she _____ it.

I was just going to move away the heavycase but someone _______ it. Was it you

Tourists can choose to visit Kunming __________ they like – spring, summer, autumn or winter.

His sister left home in 1998, and ________ since. [ ]