直放站下行标称增益（）dB。
A、50
B、55
C、60
D、65
参考答案：C
I have warned him ______ that, but he didn't listen to my warning. [ ]
A. don't do
B. not to do
C. to not do
D. don't to do
客亦知夫水与月乎？逝者如斯，而未尝往也；盈虚者如彼，而卒莫消长也。盖将自其变者而观之，则天地曾不能以一瞬；自其不变者而观之，则物与我皆无尽也，而又何羡乎？
——选自《前赤壁赋》
为什么说这里的“水”与“月”既是例证又是喻证？
