AB是（ ）线。 A:铅垂线 B:正平线 C:水平线 D：侧平线http://image.zhihuishu.com/zhs/onlineexam/ueditor/201811/43d2ca2f41b14adcb97c1eb26a8f6218.png

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" />

线、面相交正确的投影图正确是 （ ） A: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/201910/347921ea188e4488849c59bcab8d0de8.png" /> B: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/201910/8b5ae8a84e6d4de492bc48ed34745c9c.png" /> C: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/201910/f17e955e47a14fb8a5ca410f28eb60d7.png" /> D: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/201910/db67dba91b6846739c0439391bf502dc.png" />

选择图示直线相对投影面位置。（） A: 正平线 B: 侧平线 C: 铅垂线 D: 正垂线

根据所示投影图判断直线和平面与投影面的相对位置，直线AB 为何种位置直线？<img src="http://image.zhihuishu.com/testzhs/onlineexam/ueditor/201704/1f911495371d49ca82f646484054732f.png" /> A: 直线AB是侧平线。 B: 直线AB是水平线； C: 直线AB是正平线；