Complete the following exercise with past modal verbs. Use the correct form of the verbs in parentheses. Choose between affirmative and negative.
I got a C on my math test. I ____________ (should / do) better than that.
Don't be so hard on yourself. It ______ (may / be) your fault.
Don't be so hard on yourself. It just ______ (could / be) a more difficult test than usual.
The rest of the class did pretty well. I _____ (should / study) harder.
What you _______ (could / do) differently?
No, I _________ (ought to / copy) them.
Some of the problems which I got wrong ________ (must / come) from that day.