The answers are close so, #1 would not make much sense. Coasts are exactly where land and water meet so... #2 I guess that would also make sense since water deposits sediments and it's where land meets water. #3, um, coasts won't be exactly flat if sediments from water are brought and it's where water and land meet, so it can't be #3. It won't be #4 since the coasts are not very steep.
I would say #2 because sediments from the shelf are what keep the coast complete. You could say #3 but i honestly don't know what else to say.
