'If Anup is a member of the Animal Rights Society, then he opposes horse racing. Anup opposes horse racing, therefore he is a member of the Animal Rights Society.' Which fallacy is committed in the above argument?

The fallacy is affirming the consequent.

The conditional says if Anup is a member then he opposes horse racing.

The argument affirms the consequent, that he opposes horse racing.

From this it wrongly infers the antecedent, that he is a member.

He might oppose horse racing for many other reasons, so membership does not follow.

Affirming the consequent to reach the antecedent is an invalid conditional move.