1. There is one PC for every 32 pupils in American four times as many as there were four years
ago(主语比较)
2. There is one PC for every 32 pupils in American four times as many as DVD player(宾语比较)
3. There is one PC for every 32 pupils in American four times as many as for school teachers.(介宾
比较)
4. There is one PC for every 32 pupils in American four time as many as in china(介宾比较)