What existed originally that became the deposits of fossil fuels

I’m doing some practice exam questions for biology, and i’m not sure how to do these 3 parts to the question.

Select the correct answer. which mutation is harmful to the organism? a. a mutation allowing moths to camouflage better on blackened tree bark b. a mutation making staphylococcus aureus resistant to the antibiotic methicillin c. a mutation inhibiting human immunodeficiency virus from attaching to and entering the cell d. a mutation causing uncontrolled cell division e. a mutation giving plant leaves a bitter taste to discourage herbivores from eating them

How water is moving through the ecosystem ?