如图示并联管路，已知各支路的沿程阻力系数之比为<img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/201909/6e209020d20f4543823ce6516ae8ca06.png" />，管长之比为<img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/201909/50814fe028094040bc955d8e1542b6d2.png" />，且<img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/201909/40b4c6a9565b483590c5c7d607e7ed66.png" />，则两支管的流量之比<img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/201909/1055534bfce6426a94682ba086a5b17e.png" />=（）。<img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/201909/77815369f5cd41f3a2e68b9524b454c5.png" /> A: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/201909/0cd231eebe45465f941a0f614743e6d2.png" /> B: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/201909/7555afa5223e40bf89ca575cf7b52754.png" /> C: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/201909/1b06cd474b844644a6d97ad87d208e94.png" /> D: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/201909/d0b2bca045414236a7d1c9925a9264f2.png" />

下列积分中等于零的是 A: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/201909/beafcd1bd9a045e4bef379cba1d6c572.png" /> B: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/201909/fc2d4b861cbf43eb8a27dde67b97f680.png" /> C: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/201909/d9c33bed53f147c4b62a3f7553d496e0.png" /> D: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/201909/4e50aaa9bf42400db5b7573935fc97e4.png" />

如右图所示拉杆头的挤压面积为( )。<img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/201909/7ddd21a3a4e849f68c4d176b971c7c55.png" /> A: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/201909/df97de243a424ac58b1dc7cb70374683.png" /> B: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/201909/eab41cb13f55410ea57bc67fbf155a7b.png" /> C: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/201909/8c54a383f7e8426eb0f0f7c435a433ba.png" /> D: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/201909/9120d45143384f29aef7b86ea444f7f3.png" />

已知某网络函数单位冲激响应如图所示，则网络函数表达式可能为（ ） 。<img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/201909/1ea32deea3ff4a79adbdf2fd1d50f685.png" /> A: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/201909/3daa0643dbc0480582ecdded649049b2.png" /> B: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/201909/38da044f0efb404a840b6cad69f53996.png" /> C: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/201909/97e060f9767b46cbaa03ec6a04f8baed.png" /> D: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/201909/fc42e852a3ca49ff9fcb9d5efe69a1a9.png" />

剖视图正确的画法是 。 A: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/201909/9537d515da014e68a3d3cb450f99ad38.png"> B: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/201909/1a23c24f84774377874f0c38fd153a7e.png"> C: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/201909/f5954dedb8bd4b788a4a43c7a11266a7.png"> D: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/201909/bd015ac5086848d3876260b7aaf6bfc5.png">