Questions: How do CAM plants avoid water loss? CAM plants live only in moist, cool areas. CAM plants have a tap root, which replaces water as quickly as it is lost. CAM plants are succulents, so they contain such a high percentage of water that the sheer amount of water in the system prevents evaporation. CAM plants close their stomata during the day and open them at night.

The answer is the fourth one: CAM plants close their stomata during the day and open them at night.

Explanation for each option:

1. CAM plants live only in moist, cool areas. - Incorrect. CAM plants are typically found in arid and semi-arid environments, not necessarily moist, cool areas.
2. CAM plants have a tap root, which replaces water as quickly as it is lost. - Incorrect. While some CAM plants may have deep roots, this is not the primary mechanism they use to avoid water loss.
3. CAM plants are succulents, so they contain such a high percentage of water that the sheer amount of water in the system prevents evaporation. - Incorrect. Although many CAM plants are succulents, their water retention is not the main strategy for avoiding water loss.
4. CAM plants close their stomata during the day and open them at night. - Correct. This is the primary adaptation of CAM (Crassulacean Acid Metabolism) plants to minimize water loss. By opening their stomata at night, they reduce water loss due to lower temperatures and humidity levels, and they store CO2 for use during the day.

Summary: CAM plants avoid water loss primarily by closing their stomata during the day and opening them at night, which helps them conserve water in arid environments.