三相发电机采用星形接法时可以获得()种电压。
A.1
B.2
C.3
D.4
参考答案:B
柴胡的分泌组织为
A.体轻,质松,易折断,断面粉质,显疏松层纹B.质松而韧,横断面可见外层为海绵状物,内层为许多小室,室内有卵C.质硬而脆,断面平坦,外层白色,中间有亮棕色或亮黑色的丝线环4个D.体轻,中空,易碎,表面黄棕色半透明E.体轻,骨质坚硬,“马头,蛇尾,瓦楞身”
Roses need special care ______they can live through winter.
A.because
B.so that
C.even if
D.as