Ju.lia made a mis.take in her statement.
I believe the answer is C due to the fact that delta is built from rocks, mud, soil and moraines is built from rocks, sand, gravel and soil (I tried)
Im pretty sure you are talking about Sahel. If not my bad.
Answer:
AGAGAGAGA
Explanation:
AGAGAGAGAGGAGAGAGAGAGAGAGAGAGAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAGGGGGGGGGGGGG