I have two sentences as follows:
- We don't know what we should do if the worst case happens.
- The worse case is when the math teacher does not allow us to use calculators in the test.
I want to combine them into a single sentence. I am thinking of the following options but not sure which one is the correct one.
We don't know what we should do if the worst case happens; the math teacher does not allow us to use calculators in the test.
or
We don't know what we should do if the worst case happens---the math teacher does not allow us to use calculators in the test.
or
We don't know what we should do if the worst case -- the math teacher does not allow us to use calculators in the test -- happens.

