下列说法错误的是（　　）

A．2x＜﹣8的解集是x＜﹣4

B．x＜5的正整数解有无穷个

C．﹣15是2x＜﹣8的解

D．x＞﹣3的非负整数解有无穷个

The child with rheumatic fever must have his heart rate measured while awake and while sleeping. Why are two readings necessary ？（）

A．To obtain a heart rate that isn't affected by medication.

B．To eliminate interference from the jerky movements of chorea.

C．To ensure that the child can't consciously raise or lower the heart rate.

D．To compensate for the effects of activity on the heart rate.