______all  the homework assigned by the school the students have to work at it till midnight

A．Completing

B．To complete

C．Having completed

D．To have completed

听句子，缩写原文。（）

A．Many animals and plants would die because they cannot survive the changing environment.

B．Many animals would be slaughtered, since they fail to adapt themselves to the existing outside world.

C．Most peoplewould feel sorry for the destiny of endangered species, if they become extinct on earth.

D．Most species would react fast enough to adapt themselves to the ever-changing conditions of nature.