隧道结构构造中,( )的作用是保证洞口边坡的安全和仰坡的稳定,引离地表流水,减少洞口土石方开挖量。
A.衬砌
B.洞门
C.明洞
D.附属设施
参考答案:B
麦冬的显微鉴别特征有()
A.表皮细胞1列,根被细胞3~5列,壁木化
B.皮层宽广,散有含针晶束的黏液细胞
C.内皮层细胞壁均匀增厚,有通道细胞,外侧为1列石细胞
D.韧皮部束16~22个,木质部束木化组织连接成环
E.无髓
If it _____ rain next week, the farmers could still have a good harvest.[ ]
A. should
B. could
C. would
D. might