对于正序的对称三相电源，已知<img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201905/d469ef1a00bf4a7b9f72206db92b2722.png" />则（ ）。 A: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201905/f46f01b8a0944bf5b97b3085df4963af.png" /> B: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201905/bdc84f660db9480893ab3eb3df8c9174.png" /> C: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201905/2419acedbbc14be7b11bb6e2cb005039.png" /> D: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201905/6fabd0d71b0344b68b86a539fd0e0c9e.png" />

若x2+y2=1，则dy为（ ） A: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201905/d045b5f235a54083ab91e6f717cf00d8.png" /> B: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201905/74173c5355234874ab8cb9275865d5d6.png" /> C: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201905/bbfb37ba58fc4de0aa8688e0bb53cef5.png" /> D: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201905/f9a206c25e8c4ea1bd7b51519afd76b7.png" />

下列情况中，会产生感应电流的有： A: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201905/1e2e7b8e99294e8a824d5906dda51113.png" /> B: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201905/6081bc4ae79e452d904680d64f32af5a.png" /> C: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201905/655e36b2c61547b09b3411739b7ad3be.png" /> D: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201905/2735a230795a4cbda1a0197612327818.png" />

下列函数中不是复合函数的是（ ） A: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201905/852398e68ff74631bd3a10e9b908904b.png" /> B: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201905/b2421a13aeb94b93b18f4e7a67c2630f.png" /> C: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201905/f8c9b5fc3bc24e378a5013539240f424.png" /> D: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201905/78be77e785734fecbef1cc7dec213352.png" />

与y=x是同一个函数的是（ ） A: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201905/f86ae5251f654e2883551f545dfe08e7.png"> B: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201905/9423178e08ad4e9dbdc9367e98a5ef51.png"> C: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201905/cdc5f4144cbb469ab64328415e12a732.png"> D: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201905/c040b4fc143f484587591e1bb39b7dfc.png">

Photoshop中，图像的透明部分会表示为（ ） A: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201905/4e20cc22fa2d419b927fba9a72c9da1b.jpg" /> B: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201905/fe4f3b584da94076a934d71eb300a12a.jpg" /> C: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201905/a6f4e75987e54a8399f598f3eef69516.jpg" /> D: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201905/777cf882eb0e439b80358516831b1526.jpg" />

下列化合物中含3种类型氢原子的是（）。 A: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201905/7501f28545d94abe93cc62a510d76202.png"> B: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201905/dbf39be2e5974ed597f63245ce9e4063.png"> C: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201905/e863133a5b2f4b29b478a3853caac387.png"> D: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201905/fc4a3af44fcc472fab648697e261af14.png">

主视图是半剖视图，表达正确的一组是（）。 A: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201905/91a7aa656cee4f2dbc2d22fc7c61a7b9.png" /> B: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201905/73d7ce95bdec4beeb502d7c4332df823.png" /> C: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201905/d0de6ded70094a3d9613087b840a3c19.png" /> D: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201905/8250cbe6f2f54332ae2a27ded3de53ae.png" />

主视图画成半剖视图，左视图画成全剖视图，正确的是（ ）。 A: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201905/bb1bdf76d9584d199f5047f5721b97cc.png" /> B: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201905/8aca296f25ee462ca131ec7e9c385567.png" /> C: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201905/59d825ec69964cb3866372e4b1449321.png" /> D: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201905/aebe656202494d31ad1a0022989d9cc6.png" />

下列表达式中写法错误的是（ ）。 A: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201905/31bde206234643918287051fe28c4e0b.png" /> B: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201905/15084217534b4cb3b781b39f8e5173c5.png" /> C: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201905/2a4e96f210584cf9ba186bc6333bc03a.png" />