左心衰竭主要是由于
A．心率加快B．体循环静脉淤血C．毛细血管通透性增高D．肺淤血，肺水肿E．心室肥厚
参考答案：D
若点（p，q）在|p|≤3，|q|≤3中按均匀分布出现，则方程x2+2px-q2+1=0无实数根的概率是______．
. Jack is always occupied __________ his work, which makes him have no time to stay with his family.
A．by
B．for
C．with
D．to
