next time 前面无需加介词
这些问题是无法解释的,只是外国人的习惯问题
at作介词的几种用法
1. 在...地点
They were already waiting at the gate when I got there.
当我到达那里时,他们已等候在门口了.
2. 在...时刻
Jane will meet her boy friend at Christmas.
简将在圣诞节和她男友见面.
3. 向,朝,对着
Don't shout at me.
别对我叫喊.
4. 在...方面
He is an expert at troubleshooting.
他是位排解争端的能手.
5. 因为,由于
I woke at the sound of the bell.
随着铃响,我醒了.
6. 从事于,忙于
He is working hard at this thesis.
他正在努力地撰写论文.
7. 以(某种价格、速度等)
They sold the cloth at a dollar a yard.
他们以每码一元的价格出售这种布.