The process in which loss of water in the form of vapours from the aerial parts of plants takes place is $X$, which helps in $Y$. Here $X$ and $Y$ respectively are:

In plants, the loss of water in the form of water vapour from the aerial parts (mainly leaves) is called transpiration ($X$). Transpiration serves two major functions: it creates a suction pull (transpirational pull) that helps in the absorption and upward movement of water and dissolved minerals from roots to leaves, and it helps in temperature regulation ($Y$) by cooling the plant body.

• Why option (b) is correct: It correctly identifies $X$ as transpiration and $Y$ as temperature regulation.
• Why option (a) is incorrect: While water is a raw material for photosynthesis, transpiration itself is not the process of photosynthesis, nor is photosynthesis its primary immediate physical consequence.
• Why options (c) and (d) are incorrect: Translocation is the transport of soluble products of photosynthesis through the phloem, not the loss of water vapour from aerial parts.