听力原文：The cowbird is an unusual American bird, which builds no nest. Instead, a female

lays an egg in the nest of another bird and leaves the chicks to be hatched and raised by the adopted parents. Usually, these adopted parents don't seem to notice anything strange about the young cowbird.Even though it may be twice size of their own chicks.

What is remarkable about the cowbird？

A．The cowbird builds its nest.

B．The cowbird sits on the cow.

C．The cowbird has its own chicks.

D．The cowbird builds no nest.