Answer:
There is 10 birds on a branch, a man shot 5 of them. How many were left?
What is something yet nothing, but if you fill it up it will disappear?
A natural tattoo on babies
Sitting down you have it, Standing up you don't.
You fill it and it empties, A metaphor for plenty, Depending on what half you see, It's either full or empty
When is it bad luck to see a black cat?