Confused what’s the answer

Which kind of aquatic ecosystem does the photograph most likely show? a. marsh b. swamp c. lake d. river

Rarefaction is used for which of the following? a. creating a representative sample b. studying how disease impacts populations c. rediscovering species thought to be instinct d. determining which sea creatures live in an area

Anormal strand of dna is shown below, followed by the same strand of dna after mutations have occurred.