33. When a student asks_________it is worth staying up doing their lessons, a teacher may find it difficult to answer.
I used to quarrel a lot with my parents, but now we ________ well.
---- She looks happy. She ________ have passed the exam. ---- I guess so. It’s not difficult after all.
Scientists have to work hard to keep ________ with modern discoveries and developments.
The child was told to ________ for being rude to his uncle.
The two girls had been talking in ________ low voice all ________ time during the meeting, which upset the manager.