Water use efficiency is more when

Correct option is A

Correct answer – (a) Water use efficiency increases when more yield is produced per unit water used. Higher crop yield improves output efficiency. Thus, WUE is more when crop yield is increased.
Information Booster / Facts WUE = Crop yield / Water used (or ET). Reducing evaporation improves WUE indirectly.
Why other options are incorrect (b) Higher evaporation reduces WUE. (c) Higher transpiration increases water loss, lowering WUE. (d) Higher evapotranspiration reduces efficiency.