You need to answer honestly, because if you get caught it's non-recoverable... you got fired from a 121 carrier, and then got fired from a second 121 carrier for lying about the first one... nobody would touch you, at least nobody you'd actually want to work for.

But if you resumed your career at the same airline which terminated you, that will do a lot to mitigate the circumstances. Having a major life issue at the time is also mitigating, you should be fine in the long run although yes to that box will delay your getting called by majors.