6Kv配电变压器的一次绕组额定电压为6.3Kv时，其分接头上下可调整的范围为（）。
A.±2%
B.±5%
C.±7%
D.+10%，-7%
参考答案：B
There are many valuable services which the public are willing to pay ___, but which __ not bring a return in money to the community.
A．to; do
B．不填；does
C．for; does
D．for; do
最常见的胸部外伤是
A、气胸
B、血胸
C、单纯肋骨骨折
D、心肌挫伤
