--It’s a pity that you didn’t come to my birthday party last night.--I’m terribly sorry. I ________ for an important lecture.
________energy, we turn off the lights for Earth Hour on the last Saturday in March
American students take part in a wide variety of after-school activities _______ they develop their social skills.
Jenny is quite good at taking notes. She can _______ almost every word her teachers say in class.
---Have you read any novels written by the famous writer Mo Yan? --- Yes, of course. I ______ several of his works when I was studying abroad.
Thanks to scientific research, we now have a good understanding of ______ an earthquake is and why it happens.