Which number should replace the question mark?

Jun the 21st is International Yoga Day! Celebrate it with few Yoga jokes!

1. I recently took up yoga, and the instructor asked me how flexible I am…
I said: I can only do Fridays.

2. I'm trying to write this pun about yoga.
But it's just not working out. It just seems a stretch.

3. What does the yoga teacher want for their birthday?
All they want is your presence.

4. Where do you go if you can't afford yoga classes?
The omless shelter.

5. Why is the pear so good at yoga?
He's got a great core.

6. What did the yogi tell his dog?
Nama, stay!

7. What do you do when a yoga guru goes missing?
Nothing. They'll find themself.

8. What's a pirate's least favorite yoga move?
The plank pose.

9. What do an ambulance and a yoga class have in common?
They both contain stretchers.

10. I did an amazing yoga pose over this stream created from acidic rainfall yesterday.
I think it's called a bridge over troubled water . . .

11. Why is it easy to make an appointment with a yoga teacher?
They're just so flexible.

12. I run a meditation and yoga studio for angry donkeys.
It's called "peace of ass".

13. Why did the yogi return the vacuum cleaner?
It came with too many attachments.

14. What happens if you kill a yoga teacher before the start of class?
You get charged with premeditated murder.

15. Why are weightlifters so good at yoga?
They have great flex-ability

16. Why did the yogi refuse anesthetic at the dentist?
He wanted to transcend-dental-medication!

17. I got chucked out of yoga class yesterday.
Apparently, I misinterpreted the Half-Moon Pose.