八害道钉，歪指的是（）。
参考答案：垂直轨条方向目视道钉钉杆向左右方倾斜
表现为吸气性呼吸困难的疾病是（）
A.急性喉炎
B.支气管异物
C.毛细支气管炎
D.哮喘
E.气胸
7. Dave lost his job and was short of money, so ______his flat and move in with his brother.
A．that he did was to sell
B．what he did sell
C．what he did was sell
D．what he did sold.
