肺源性心脏病最常见的原因是（）。
A.慢性支气管炎、肺气肿
B.胸膜增厚粘连
C.肺结核
D.机化性肺炎
E.支气管扩张症
参考答案：A
With more forests being destroyed, huge quantities of good earth _____________ each year. [ ]
A. is washing away
B. is being washed away
C. are washing away
D. are being washed away
农业积累的含义是什么？
