Most used fining agent for wine is

Answer: Option A

The most used fining agent for wine is Bentonite clay.
Bentonite clay is the most widely used fining agent against heat-instable grape proteins in white wines. As it is negatively charged and dense when it does bond with a positively charged particle they both sink to the bottom of your carboy.
It is a common additive used to clarify fine wines. It's great for removing protein haze and can be used to remove aromas.