In rainforests, precipitation largely results from transpiration, where plants release water vapor into the atmosphere, leading to cloud formation and rain. This cycle is crucial for the rainforest ecosystem's health. Thus, the correct answer is d. transpiration .
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Precipitation in the rainforest mainly results from transpiration, where plants release water vapor into the atmosphere. This process leads to cloud formation and eventually precipitation. Other options like perspiration and respiration do not directly contribute to rainfall. ;