Final answer:
Transpiration is the process in which plants release excess water as vapor into the atmosphere through stomata, which are tiny pores on their leaves.
Step-by-step explanation:
Transpiration is the process where plants release water back into the atmosphere. This occurs when water vapor is lost from plant leaves through tiny openings called stomata. The water taken up by the roots from the soil is more than what the plant needs for photosynthesis and other processes, so the excess is released into the air. The energy driving transpiration is the difference in energy between the water in the soil and the water in the air around the leaves. At night, this process slows down as stomata close, which helps the plant retain water.
Answering the multiple-choice question, Transpiration is the process where: b. plants release water.