生狗脊片近外皮1~4mm处有一条凸起的棕黄色环纹是()
A.韧皮部
B.木质部
C.石细胞环带
D.形成层
E.纤维层
参考答案:B
. It’s a miracle that Mike ____the final exam last week.
A.might have passed
B.should have passed
C.would have passed
D.could have passed
300MW机组调节汽门关闭时间应小于()毫秒。
A.300
B.400
C.50
0D.600