Translocation of sugars from source to sink (B) is not a purpose of transpiration.

Explanation:
Transpiration is the process by which plants lose water vapour through their leaves, which helps to create a negative pressure gradient that pulls water and minerals up from the roots to the leaves.

A, C, D options are purposes of transpiration because
A. We saw that transpiration helps pull water and this water is used in photosynthesis.
C. Transpiration maintains the shape and structure of the plants by keeping cells turgid.
D. Transpiration helps pull minerals as well along with water. Thus D is also a purpose.

But, Transpiration does not directly play a role in the translocation of sugars from source to sink, thus B is not a purpose of transpiration and is the correct option.