题目内容：

 

1.Columbus _________ （发现）America but didn’t explore the new land.

2.I ___________（承诺）I won’t be late in the future, you must believe me.

3.It seems that your words don’t __________ （奏效）.

4.He has ____________（从事）medicine for a year.

5.Get up early, ____________（否则）we will be late again.