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

To express a subordinate future action that happens AT THE SAME TIME as a primary future action, we use the SIMPLE PRESENT TENSE:
The band will play WHEN THE OPPOSING TEAM ARRIVES.
Here, the simple present tense verb in blue serves to express an action that happens at the same time as the primary future action (the band will play).

To express a subordinate future action that is completed BEFORE a primary future action, we use the PRESENT PERFECT TENSE:
The play will begin AFTER THE AUDIENCE HAS BEEN SEATED.
Here, the present perfect tense verb in blue serves to express an action that is completed before the primary future action (the play will begin).

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.

In A, the usage of after is correct, but the tense of the following verb is not.
Since the act of trimming the horns is a subordinate future action completed before the primary future action (tourists will continue to visit), the present perfect tense is required:
Tourists will continue to visit after the horns HAVE BEEN TRIMMED.

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

Please help

Thanks

In E, it is unclear whether one serves to refer to one RHINOCEROS or to one GAME PARK.
Since C avoids this ambiguity and is free of errors, eliminate E and choose C.