按发生机制，双吸气见于哪类呼吸困难
A．肺源性
B．心源性
C．中毒性
D．呼吸中枢性
E．精神性
参考答案：D
—What did Eric _____ last Sunday?
—He _____ a film with Mike. [ ]
A. do; sees
B. do; saw
C. do; was seeing
D. did; saw
滑步
