Don't stay ( ) too late. You'll have a busy day tomorrow.

Don't stay ( ) too late. You'll have a busy day tomorrow.
A、in
B、at
C、on
D、up
【正确答案】：D
【题目解析】：固定短语stay up 熬夜，句子含义是不要熬夜太晚，明天是忙碌的一天。