I didn’t quite follow him because he explained the theory _____that is too abstract for me.
______ it is to listen to music when you are free.
—What are you going to do this weekend?—_______. If time permits, I may go to Shanghai with my friends.
I hope there are enough glasses for each guest to have ______.
Professor Smith, along with his assistants, _____ on the project day and night to meet the deadline.
With a lot of difficult problems ______, the newly-elected president is having a hard time.