It is an oversimplified view of cattle raising to say that
all one has to do with cattle is leave them alone while they feed themselves, corral them, and to drive them to market when the time is ripe.
(A) all one has to do with cattle is leave them alone while they feed themselves, corral them, and to
(B) all one has to do with cattle is to leave them alone to feed themselves, to corral them, and
(C) all one has to do with cattle is leave them alone while they feed themselves and then corral them and
CORRECT.
All one has to do with cattle is leave them alone while they feed themselves
and then
corral them and drive them...
It's well-written in active voice
(D) the only thing that has to be done with cattle is leave them alone while they feed themselves, corral them, and
This answer choice is worse than (C) for the following reasons:
1) Passive voice
2) "thing" is very informal and more incorrect than correct on the GMAT
3) the list doesn't consist of "things" but ACTIONS. Therefore, "thing" isn't really the right noun to describe what's needed in this context
4) sentence would've been better if it had "to" before leave
(E) the only thing that has to be done with cattle is to leave them alone while they feed themselves, to corral them, and