He found it very difficult____________(赶上)the development of physics.
举一反三
- He found it very difficult ______. A: sleeping B: sleeps C: slept D: to fall asleep
- Some subjects, such as physics and biology, are very difficult to learn.
- They found it was very difficult to ____all these problems.(cope with)
- I found it very difficult to answer the question.
- They found it was very difficult to ()all these problems. A: add to B: cope with