Option D is the correct answer because “zephyr “ literally has the dictionary meaning of a soft, gentle breeze, hence it is correct.
Option A is incorrect because “wind” means the perceptible natural movement of the air, which is not the same as a soft gentle breeze, hence it is incorrect.
Option B is incorrect because “squall” means a sudden violent gust of wind or localized storm, which is the opposite of a soft gentle breeze, hence it is incorrect.
Option C is incorrect because a draft means a preliminary version of a piece of writing, and a draught means a current of cool air in a room, both of which are incorrect for a soft gentle breeze, hence it is incorrect.