Question 1:
The answer is d. none of the above.
All mentioned factors contribute more or less to water pollution. Forestry, by removing trees from some area, increases the risk of erosion. The industry is a great water pollutant. Its facilities throw away waste into the water. Agriculture affects water quality by degrading Earth's surface and groundwater through erosion.
Question 2:
The answer is d. breathing apparatus on the top of the head.
Sea otters live both on land and in the water. They have streamlined body and webbed hands and feet, like the other marine mammals. They also have a thick fur. Since they can live on the land, they don't have breathing apparatus on the top of the head, like the other marine mammals (dolphins, whales) that cannot leave out the water.
