1942年，美国生态学家林德曼提出（）。
A.食物链
B.生态金字塔
C.生态学
D.生态系统
参考答案：A, B
The doctor insisted I ____ a high fever and that I ____ a rest for a few days. [ ]
A. had; had
B. have; have
C. had; have
D. have; had
穴蚀或称为（）。
A．空泡腐蚀
B．点蚀
C．腐蚀
D．锈蚀
