地球上面积最大的生态系统是 ( )
A．森林生态系统
B．海洋生态系统
C．农业生态系统
D．生物圈
参考答案：D
I won the first prize and you can imagine how excited I was when the Mayor _____ me
with the reward. [ ]
A. provided
B. supplied
C. presented
D. charged
二尖瓣型P波伴右室肥大心电图改变最常见于（）
A.二尖瓣狭窄
B.二尖瓣关闭不全
C.高血压心脏病
D.冠心病
E.肺心病
