I'm most likely too late but I'll answer it anyways.
The answers are Hydrothermal vents, and Rifts.
Reasoning: Hydrothermal vents are basically splits in the ocean floor reaching down to the mantle, it being caused by diverging plates makes sense.
Continental mountains are wrong and I don't think I need to explain why.
Ridges are basically a long line of peaks (sort of) it's not something diverging plates would cause.
Subduction trenches are formed from subduction zones from one plate folding under another which can only happen if there is a convergent boundary.
Rifts are basically long splits in the ground, like ridges but inverted, this is the second correct answer.
Hope this helps.