for a while是什么時態的標志

　　A back injury prevented active participation in any sports for a while.

　　背傷曾一度妨礙積極參加任何體育運動。

　　I think you'd better lay off fatty foods for a while.

　　我認為你最好暫時別吃高脂食物。

　　Go and lie down for a while.

　　去躺一會兒吧。

　　We're going to be minus a car for a while.

　　我們要過一段沒有車的日子。

　　Come and sit down and take the weight off your feet for a while.

　　來坐下歇一會兒吧。