[译] 夜里，温度急剧下降。
[误] The temperature dropped sharply at night.

[正] The temperature dropped sharply in the night.
[注] at night 指任何晚上，是泛指。例如: They watch TV at night. 他们常常晚上看电视。in the night 指一个特定的晚上 (during one particular night)。例如:They watched TV in the night. 他们晚上看了电视。