正确答案：BD
解析：
Mother elephants don't completely let little Dumbo go out of their sight (an adult is nearby), but the mothers do offer young calves a small degree of freedom. (D) clearly works. A synonym, (B), means the freedom to move about, either in action of thought (in this case, it is action).

(A) means to dismiss somebody. The young calves, however, are still with the mothers; they are just not standing next to them.

(B) Answer.

(C) An incentive is something that motivates someone to follow an action. Is not supported by the context.

(D) Answer.

(E) Means to give a little punishment, a tap on the wrist (or the trunk, as it were).

(F) Means guidance. This doesn't really match up with the context since nothing in the sentence is really guiding the young calf.