Similarities:
They contain nematocyst (cells that sting)
some are sessil/free swimming
Some corals have a symbiotic relationship with algae, they need to grow in shallow waters so that light can penetrate for the algae to photosynthesize.
The good thing about a dam is that electricity can be created by mechanical means. That does not affect the atmosphere. Storing such production is a different matter.
The bad thing about a dam is that it wreaks havoc on the land where the water is stored behind the dam.
I will go with choice (C) density dependent pattern
Hypotonic (assuming that the solution on the outside is the same solution on the inside)
