A popular beach has long had a dolphin feeding program in which fish are given to dolphins several times a day; many dolphins get as much as half of their food each day there.  Although dolphins that first benefit from the program as adults are healthy and long-lived, their offspring have a lower life expectancy than offspring of dolphins that feed exclusively in the wild.

Which of the following, if true, most helps to explain the lower life expectancy of offspring of dolphins feeding at the beach compared to other young dolphins?

(A) Sharks that prey on dolphins are less common in the open seas off the beach than in many other areas of the open seas where dolphins congregate(聚集).

(B) Many of the adult dolphins that feed at the beach are females that nurse their offspring there.

(C) The fish given to the dolphins at the beach are the same types of fish that dolphins typically catch in the wild.

(D) Many dolphins that feed at the beach with their offspring come to the beach only a few times a month.

(E) Adult dolphins that feed at the beach spend much less time teaching their offspring how to catch fish in the wild than do other adult dolphins.

請問這道題爲什麽選E? 那些dolphin少了捕魚的能力就會使它平均壽命減少嗎? 這裡沒有說它要去競爭吃的丫~~求解..