着床前的胚胎易发生（）

A．生长迟缓

B．受精卵死亡

C．致畸作用

D．母体毒性

E．母体死亡

If we don’t take steps, some rare animals, such as the Tibetan antelopes and pandas will ____________ some day just as dinosaur.

A．die out

B．die away

C．die down

D．die off