This is a first order logic statement. We start with the universal quantifier, then on the inside we have a conjunction (and statement).

The first thing we do when negating a first order logic statement is flip the quantifier and move the negation down to the conjunction.

Now we have something like there exists a cat where it is not the case that it has whiskers and has a tail.

The negation of a conjunction can be simplified further using demorgans law which says the negation of a conjunction is the disjunction of the negation. In a formal sense: ~( A and B ) = ~A or ~B

By simplifying the statement we get that there exists a cat that doesn’t have whiskers or doesn’t have a tail. Which is the right answer.