1.He awoke to the ringing of an electric bell.这句话中的 ring为什么用

1.He awoke to the ringing of an electric bell.这句话中的 ring为什么用ringing?
2.Mary is a spoiled girl.很明显spoiled是个形容词,我想知道关于这一点的具体英语说法.
3.John was so sleepy that he could hardly keep his eyes open.这句话中为什么最后的词用open呢?to open为什么不能用?