We know that sec(x) is equal to cos(x) because it is the reciprocal of cosine.

So, choice d cannot be correct because cos(x) cannot be 0, because it would result in an undefined answer.

We we know that cosine is adjacent/ hypotenuse. Of course, the reciprocal would be hypotenuse/adjacent.

If if you look at choice b, c, and e, the numerators (hypotenuse) are all smaller than the denominator (adjacent side). This is not possible because the hypotenuse in a triangle cannot be less than one side.

this is why choice A must be correct