Sentence Correction

A proposal has been made to trim the horns from
rhinoceroses to discourage poachers; the question is
whether tourists will continue to visit game parks and
see rhinoceroses after their horns are trimmed.
(A) whether tourists will continue to visit game
parks and see rhinoceroses after their horns are
(B) whether tourists will continue to visit game
parks to see one once their horns are
(C) whether tourists will continue to visit game
parks to see rhinoceroses once the animals'
horns have been
(D) if tourists will continue to visit game parks and
see rhinoceroses once the animals' horns are
(E) if tourists will continue to visit game parks to
see one after the animals' horns have been trimmed

Hi Experts,

My doubt:

After is an optional marker for present perfect and by its meaning even it can be used
to segregate two different time frames.

Now in option A: why is the usage of after incorrect.
Doesn't that clearly indicate tourists should visit after ..that is-- once the animals' horns have been trimmed

What if we replace--are trimmed with "were trimmed"...does that make sense then.

Also explain me the usage of 'one' in option E.

Please help

Thanks