– You look very tired this morning. What did you do last afternoon?

-- I did _______ Christmas shopping.

A．a number of

B．a few of

C．a lot of

D．a piece of

计算机正确的开机顺序是：（）

A、先开显示器，后开主机

B、先开主机，后开显示器

C、先开主机或先开显示器都一样

D、只开显示器