A．It is to determine which food chain is the most efficientB．It is to describe the food network among plants and animals.C．It is to explain the process of photosynthesis (光合作用) in green plants.D．It is to appeal to conservationists to protect endangered plant species.
A．It is to determine which food chain is the most efficient
B．It is to describe the food network among plants and animals.
C．It is to explain the process of photosynthesis (光合作用) in green plants.
D．It is to appeal to conservationists to protect endangered plant species.