Mary____ a math problem with her classmates when the math teacher knocked at the classroom door．（ ）
| A． |
has discussed |
B． |
was discussed |
| C． |
was discussing |
D． |
discusses |
Jim， what did I say just now？
Sorry， I don't know． I _________ the math problem．（ ）
| A． |
think about |
B． |
thought about |
| C． |
was thinking about |
D． |
has thought about |
He is too lazy so he _________ does housework． We shouldn't learn from him．（ ）
| A． |
almost |
B． |
hardly |
C． |
probably |
D． |
exactly |
Jane， I saw your mother yesterday．
It _________be her． She is working abroad．（ ）
| A． |
mustn't |
B． |
can't |
C． |
shouldn't |
D． |
couldn't |
_________she is very young， she can take good care of herself．（ ）
| A． |
If |
B． |
Unless |
C． |
Since |
D． |
Although |
Parents always _________us not to swim in the river in summer．（ ）
| A． |
promise |
B． |
train |
C． |
warn |
D． |
show |