选择正确的答案。

    Helen likes birds very much. On a Saturday morning, she goes to a pet shop to buy a bird which can sing. The shop keeper sells her a nice bird and Helen takes it home. Then, she finds the bird has a broken (断的) leg. She goes back to the shop and says to the man, "One of the bird's legs is broken."

    "Miss," he answers, "When you buy the bird, you ask me to give you a singer, not a dancer."