A.50mm B.100mm C.150mm D.200mm
A.1.5倍 B.1.8倍 C.2.0倍 D.2.2倍
A.流量大、揚(yáng)程大 B.流量大、揚(yáng)程小 C.流量小、揚(yáng)程大 D.流量小、揚(yáng)程小