Explanation:

• Option 1 is correct- Oxygen is the most important gas in the atmosphere. Without oxygen, there would be no life on the earth. In polluted waters amount of dissolved oxygen often gets reduced (due to excessive consumption by bacteria's to break down organic matter) leading to the death of aquatic organisms.
• Option 2 is correct- Oxygen is less soluble in warm water. Warm water also increases the rate of decomposition. Thus increasing temperature of water body increases oxygen depletion
• Option 3 is correct- Sunlight is necessary for primary producers to carry out photosynthesis. It is the ultimate energy source. This is the reason why deep ocean (devoid of sunlight) have less biodiversity or whatever that is based on Chemosynthesis.
• Option 4 is correct- If too much of organic matter is added to water, all the available oxygen is used up. This causes oxygen dependent aquatic life to die. Thus excessive organic matter will disturb the aquatic food chain, resulting in low aquatic productivity.