The two boys look so much alike _______no one can tell them apart.
It’s too bad that I failed in the math exam. If only I ______ hard at it!
The last decade of the 21st century ________ the rapid, steady development of China in various fields.
---He should have been warned of the danger.---_______, but he wouldn’t listen to me.
The teacher asked the two students to discuss the question in a low voice ________ they should bother the others.
It was in the lab ___was taken charge of by our teacher____ they did the experiment.