好难的一道语法题，请大家指点

寂寞的自由

21. ！！！（难！）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.D----》C
(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
(D) the only thing that has to be done with cattle is leave them alone while they feed themselves, corral them, and
(E) the only thing that has to be done with cattle is to leave them alone while they feed themselves, to corral them, and

正确答案是C，自由这次没蒙对！请大家帮忙分析一下5个选项，感谢！！！

zida

all one has to do with cattle is leave them alone while they feed themselves and then corral them and-----parallels after is: leave, while feed, then corral, and drive. In D, two commas make it not all "one" has to do. Comments?