For this item, I would go with letter "D. physical destruction of marine habitats". Many of the modern ways of fishing poses an irreversible destruction to marine habitats. These practices include trawling, lining methods, purse seining, etc.
The answer is D cuz I just looked up a lot of it and saw the pics so ya its D
The smallest dna fragments are located near the bottom of the gel. (Positive electrode)
The largest dna fragments are located near the top of the gel. (Negative electrode, where they began)