用所给单词的适当形式填空。   

1. Tom______(swim) for two hours in the river.

2. When______you______(buy) the new computer?

3. When I entered the classroom, I found some students______(watch) TV.

4. There are some children who______(play) football on the playground.

5. —How long______ you______ (do) that?

    —For about five years.

为应对失业率居高不下的困境，美国联邦储备委员会两次启动量化宽松政策，总共过量发行2万亿美元。如果不考虑其它因素，此举对我国经济的影响有

①以美元核算的外汇储备较大幅度增长②以美元核算的外汇储备较大幅度缩水

③以美元计价的出口企业利润增加   ④以美元计价的出口企业利润减少

A．①④    B①③    C②④    D．②③