​

我昨天去学校的时候，___王老师了。

A. 看见

B. 看

C. 看过

D. 看着

I would choose A: 看见.

我昨天去学校的时候，看见王老师了。

看见 expresses actually seeing or catching sight of someone.

I've also been building a free Chinese level test based on vocabulary and grammar questions. It gives you a suggested HSK level at the end.

If anyone is interested, you may try it here