Statements:

I. All zebras are horses.

II. All horses are donkeys.

Which conclusion logically follows?

(A) All zebras are donkeys

(B) All donkeys are zebras

(C) Some donkeys are zebras

(D) Some horses are zebras

I. All zebras are horses.

II. All horses are donkeys.

Since all zebras are horses and all horses are donkeys, all zebras must also be donkeys. This conclusion logically follows.

This does not logically follow.  "Donkeys" circle is the largest and contains the "Horses" and "Zebras" circles. Therefore, not all donkeys are zebras.

Since all zebras are horses and all horses are donkeys, it follows that some donkeys (those that are horses) are zebras. This conclusion logically follows.

Since all zebras are horses, it follows that some horses are zebras (in fact, all zebras are horses). This conclusion logically follows. 

Thus, the correct option is (c) A, C, and D follow.