queuing principle

例句：

1. 1. The customers were queuing at the entrance of the supermarket.
   顾客们在超市入口处排队。
2. 2. The employees were queuing for their shifts.
   员工们正在排队等待他们的班次。
3. 3. The students were queuing to get in line for the free snacks.
   学生们排队领取免费的零食。