某种乔木生于密林中比生于疏林中更高更直，这主要是哪种生态因子在起主导作用？（）
A.光
B.温
C.水
D.气
参考答案：A
He is very popular among his students as he always tries to make them ____ in his lectures. [ ]
A. interested
B. interesting
C. interest
D. to interest
下述不是大量心包积液X线主要表现的是( )
A．心弓切迹消失B．上腔静脉增宽C．心尖搏动位于心影内D．心搏动减弱E．肺动脉高压
