For the engine to work, the green button be in the “on” position.
I hate ______ when people call me by my nickname (绰号).
Can you see that building ______ by trees? That’s ______ we study.
Sir, you ________ take this seat. It’s just for the old.
______ life began on earth is one of the biggest puzzles that scientist found hard ______.
Was it because his mother was ill ______ he didn’t go to school?