他们发烧了,他们必须卧床.用英语翻译.

They are hava a fever ,they are must stay in bed.

他们发烧了，他们必须卧床。
They've had a fever right now, thus they have to stay in bed.
Since they've got a fever, they must take a BR(bed rest) at this moment.
They have a temperature, therefore they're forced to (take a可要可不要) rest in bed.
。。。
说明：两句存在（因果）关系，故相应添加连词
供参

They have a fever ,so they have to lie down and rest.
(*^__^*) 嘻嘻……刚学完不久。。

【They are having a fever. They have to stay in bed.】

希望帮到你，祝学业进步！
若有疑问及时追问，满意敬请采纳，O(∩_∩)O谢谢~~

They have a fever,they must stay in bed.
They have a fever,they must have a rest in bed.
两种说法都可以额

Having a fever, they have to stay in bed.