How could the Klingon captain have survived being blasted to bits by the Borg?
If were going to get into could so-and-so really have survived discussions, we could be here for weeks. But, OK, OK Young MiQoch survived because 1) Klingons are wicked hard to kill and 2) His ship had an extended life support system on the bridge that would continue to work marginally and seal off minor hull breaches allowing him to stay alive. Or perhaps he was saved by a special, but highly secret type of instrumentation thats present on every starship in the Alpha Quadrant, known as a plot device. When activated it ensures that no continuing character gets killed.
