It was not until I failed in the test ______ I realized I had wasted too much time instead of preparing for it fully.
All those second-hand goods are sold at ____ before.
——The switch to more low-carbon energy, I think, is _____. ——I agree with you.
Many a student ____ going to have themselves ____ in the hospital.
Three minutes earlier ____ we could have caught the early train to Philadelphia.
Many people have been ill from a strange disease these days, _____ we’ve never heard of before.