Age / Determiner
We should leave early.
Recommendation
I want a red beautiful ball.
Wrong; adjectives changed.
They ___ place their car on the road.
can
Opinion / Origin
Opinion - Origin
She can do it.
Ability
My beautiful lazy daughter is at her house.
Wrong; comma necessary.
___ I leave early? (polite)
Could
Origin / Size / Shape
Size - Shape - Origin
Past ability
There's a green Irish leprechaun at the store.
Right
I ___ work on it now.
can
Color / Material / Shape
Shape - Color - Material
Could you do the chores for me?
Your big red american car is amazing.
Wrong; origin adjective should be in capitals
could
Age / Color / Purpose / Size / Shape
Size - Shape - Age - Color - Purpose
Can I speak?
Informal permission
Daniel has three funny big old plastic toys.
Right
___ I use the bathroom? I ___ not go before. (formal)
May; could