农田生态系统的生产力水平较高是因为增加了（）
A、腐食食物链
B、捕食食物链
C、寄生食物链
D、其它
参考答案：B
—I feel stressed in my study from time to time. I don't know what to do.
—_________.[ ]
A. You should keep relaxed.
B. What about keeping your worries to yourself?
C. Why not ask the youth workers for advice?
D. You'd better pay no attention to your study.
在社会主义市场经济条件下，要保持币值的稳定，就必须使货币流通量等于商品流通的需要量。 ( )
