My father usually goes to work . [ ]
A. by a car
B. on a car
C. in car
D. by car
D
下列哪些是防风的性状特征()
A.根圆柱形
B.根头部是“蚯蚓头”“扫把头”
C.体轻、质松、易折断
D.断面可见裂隙或“朱砂点”
E.气香特异
怎样才能消除高压、超高压机组热态启动时的转子相对收缩和转子的热挠曲以及汽缸的热挠曲?