For our middle school students, some courses are compulsory, while others are ________.
| A．flexible | B．optional | C．impressive | D．significant |
He insisted that the sky ____ clear up the following day.
| A．would | B．should | C．／ | D．be |
You should treat him (in) the way ____ suits him most.
| A．that | B．in which | C．/ | D．why |
--- How long have you been here?
--- _____ the end of last month.
| A．In | B．By | C．At | D．Since |
We keep in touch ____ writing often.
| A．with | B．of | C．on | D．by |
Who is it up _____ decide whether to go or not?
| A．to to | B．for for | C．to for | D．for to |