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.
Option Elimination -
(A) all one has to do with cattle is leave them alone while they feed themselves, corral them, and to - we have verbs "leave," "corral," and then a verbal (infinitive) "to drive" - not parallel. Moreover, the intended meaning is leaving them alone is one activity (as they don't need anyone while feeding themselves), and corraling them and driving them is part of the 2nd action -think of it like this before you take them to the market: what will you do? Will you group them together (corral them) and then take them to market? Right? Yes. And not take them one by one, which is a very inefficient way. That's why "corral and drive are together, and feeding them is another separate action.
(B) all one has to do with cattle is to leave them alone to feed themselves, to corral them, and - two "to verbals" and one verb. Not parallel.
(C) all one has to do with cattle is leave them alone while they feed themselves and then corral them and - "then" is good as it separates the two actions. Ok.
(D) the only thing that has to be done with cattle is leave them alone while they feed themselves, corral them, and - mess up. " the only thing that has to be done" means there is only one thing, but there are three. Moreover, the pairing of verbs is a mess.
(E) the only thing that has to be done with cattle is to leave them alone while they feed themselves, to corral them, and - same issue as D. Moreover, a sprinkle of "to verbal" and verb mess as well to create a perfect wrong answer.