倾斜井巷中使用的带式输送机，上运时必须同时装设防逆转装置和（）装置；下运时必须装设（）装置。

----What did you say just now ?

----I asked you________.

A．why you wanted to become a nurse

B．how long had you stayed in the town

C．whether was there a bank near our school

D．when will you go shopping with me