环境问题包括环境污染和生态破坏。……………………( )
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The city wall of Pingyao Ancient City is 46 kilometers. It is about 10 meters high and 3 to 6 meters wide on top.
A. 对
B. 错
The layout of the ancient city looks like a giant dragon because Chinese are the offspring of the dragon.
A. 对
B. 错
People in Pingyao wish the ancient city would be safe and secure for thousands of years just like the kylin.
A. 对
B. 错
下面( )不是PD校正的作用
A. 减小带宽,响应速度减慢。
B. 稳定裕量增加, 稳定性增强。
C. 增大剪切频率ωc,使带宽变大,响应的快速性提高。
D. 使系统的高频增益增大,系统抗干扰能力降低。