Answer:
You did not give the selections and there are two questions that fit this one so I will just give you an idea.
Biotic factors are factors in an ecosystem that are living things. Bio- means life, which means biotic factors are living organisms.
Taking this into account, anything that has life like plants and animals are biotic factors. Some examples of biotic factors that influences coastal plains, (that might be one of your choices as well) would be:
beach grass
Live oak trees