经过整流最接近直流的整流电路是（）。
参考答案：三相桥式电路
---Imagination important in science, and it helps us dream up our future.
---You are definitely right. If only something allow me to see insects and spiders magnified without getting close to them.
A．was; would
B．is; will
C．will be; can
D．is ;could
下列哪两组实验的结果能够说明，光合作用产生的氧只能来自水（）
A.①②
B.①③
C.②③
D.②④
