下列哪些接线为变压器一次与二次绕组相差60度.（）
A、Y/Y-2
B、Y/Y-10
C、Y/Y-12
D、Y/Y-8
参考答案：A, B
You ______ to the meeting this afternoon if you have something important to do. [ ]
A. needn't to come
B. don't need come
C. don't need coming
D. needn't come
由于伦理方面的原因，目前尚未在人类身上成为现实的辅助生殖技术是( )
A．代孕技术B．同源人工授精C．异源人工授精D．无性生殖E．体外授精
