The last one...the species is unable to reproduce in any habitat beyond a population of 300 individuals
C...the key is that they are photosynthetic...so they produce oxygen (like plants)!
I believe you mean mid-ocean ridge?
If so, true.
A mid-ocean ridge or mid-oceanic ridge is an underwater mountain range, formed by plate tectonics.
This uplifting of the ocean floor occurs when convection currents rise in the mantle beneath the oceanic crust and create magma where two tectonic plates meet at a divergent boundary.
A mid-ocean ridge demarcates the boundary between two tectonic plates, and consequently is termed a divergent plate boundary.