A client with heart failure asks the nurse about the reason for taking enalapril maleate. The nurse would explain that the medication is prescribed for which of the following reason

A．Lower the blood pressure by increasing peripheral vasoconstriction.

B．Lower the heart rate by slowing the conduetion system.

C．Block the conversion of angiotensin Ⅰ to angiotensin Ⅱ.

D．Increase myocardial contractility, thereby improving cardiac output.

当前我国污染严重，生态环境恶化已经成为突出的（）。

A.政治问题

B.经济问题

C.民生问题

D.社会问题