上课困乏用英语怎么说

"上课困乏"可以用英文表达为"feel drowsy during class"。
"Drowsy"是形容词，意思是困倦的，疲倦的。"During class"是介词短语，意思是在上课的时候。
下面是一些例句：
I often feel drowsy during class because I don't get enough sleep at night.
The lecture was so boring that I couldn't help feeling drowsy during class.
I had a hard time staying awake during class because I was feeling drowsy.
以下是这些例句的中文翻译：
我经常在上课的时候感到困乏，因为晚上没有充足的睡眠。
这个讲座太无聊了，我忍不住在上课时感到困倦。
我在上课时很难保持清醒，因为我感到困倦。