1 . ______ is acknowledged to us all that the old scientist, for whom life was hard in the past, still works hard in his eighties. (用适当的词填空)

2 . I owe_________ to you that I finished my work in time. （用适当的词填空）

3 . It suddenly occurred to him _____ he had left his keys in the office.

4 . The other day, ________ occurred to Johnson that he should make a road trip to help the needy. (用适当的词填空)

5 . If you can’t make____________ next Friday, we can invite somebody else. (用适当的词填空)

6 . It’s a challenge for me to ______ (memory) 50 new words per day. （所给词的适当形式填空）

7 . Susan made________ clear to me that she wished to make a new life for herself. （用适当的词填空）

8 . _____is known to us all that the 2022 Olympic Winter Games will take place in Beijing. (用适当的词填空)

10 . You can rely on ________ that the Belt and Road initiative will lead into a new era of prosperity. (用适当的词填空)