我国沿海地区气象灾害多、损失重,每年平均有()个热带气旋(含台风)登陆我国,对经济社会和人民生命财产安全构成严重威胁。
A.5
B.7
C.10
D.12
参考答案:B
He was _ busy that he forgot to have supper yesterday. [ ]
A. too
B. very
C. so
D. quite
试述有髓神经纤维的组织结构。