She has to be in bed by ten o'clock

She has to be in bed by ten o'clock
She has to be in bed by ten o'clock

She has to be in bed by ten o'clock
她十点之前必须睡觉

她十点前必须睡觉。

截止到十点， 她必须呆在床上。

她十点前必须睡觉。