缓解肺气肿患者呼吸困难的首选措施是（）
A．胸腔引流
B．通畅呼吸道，持续低流量吸氧
C．镇静剂
D．强心剂
E．呼吸兴奋剂
参考答案：B
The problem is hard but Tom has _____ a good idea to solve it.[ ]
A. caught up
B. come up with
C. caught up with
D. came up with
