(What do you think is the hardest job and why?)

I think fire fighter is hardest job.
> I think fire fighter is the hardest job.

Because fire is dangerous
(This is correct.)

fire fighter is not sleeping everyday
And, the fire fighters have lack of sleep.

Thank you for making your homework, Kelly. Thank you for trying your best to think of a good sentence. Keep it up! ^^ Study well and always practice your English even at home.

See you and have a good sleep tonight.

~Teacher Cassie