Their idea was to get us to the strike at once.A. call at B. call off C. call in D. call for

同时: all at once|all once|at all once|at once

The manager ordered the work ______. A: start at once B: to be started at once C: to start at once D: at once started

He ordered the work (). A: started at once B: to be started at once C: to start at once D: at once start

The phrase "once in a blue moon" in last line refers to______. A: all at once B: once for a long time C: once in a while D: once and for all

How often will the woman correct the students’ assignment A: Once a week. B: Once two weeks. C: Once a month. D: Once three weeks.

Michael was always late for class, but that day he, _______ , came much earlier than usual. A: for once B: at once C: once D: once again

Riddle: What is it that occurs once in a second, once in a month, once in a century, yet not at all in a year or a week?

All of the plants on farms have been developed from plants _______ wild. A: once they grew B: they grew once C: that once grew D: grew once

All of the plants now raised on farms have been developed from the plants _____ wild.​‌​ A: once they grew B: they grew once C: that once grew D: once grew