用方框中所给单词的适当形式填空，每词仅用一次（每空一词）。

小题1:My son wants to go to see the          in the zoo. He thinks they are lovely.

小题2:Mr. Green ______ English in No. 1 Middle School when I was ten years old.

小题3:Do you know that Bill Gates donated（捐赠）____4____ of dollars in 2010?

小题4:If we work hard ,we will          at last.

小题5:He had to talk to          when there was nobody at home.

PCM脉冲编码调制，它是一种将（）数字化的过程。