My friend Derek is a model, but right now he __________________________ as a coal miner.
1. works
2. is working
Permanent state: he is a model.
Temporary situation: he is working as a coal miner.
Did you know that octopuses ____________________ three hearts?
1. have
2. are having
It's a scientific fact. It's always true. So use the present simple.
How often ________________________ your legs in the shower?
1. do you wash
2. are you washing
It's a habit (or it should be!) so it's a present simple situation.
Did you know that there was a huge internet debate about whether you should wash your legs in the shower or not? A lot of people don't do it.
What would you say to this lady?
1. "You watch too much TV!"
2. "You're watching too much TV!"
Maybe she watches a lot of TV in general (present simple) but she's certainly watching too much right now (present continuous).