Answer:
I can be simple or I can be complex. I can be found in this riddle or in everyday life. I can be shapes or even colors.
People need me, yet they give me away every day. What am I?
With three leaves, I am just a plant. Add another leaf and everyone will want me for good luck. What am I?
I transfer oxygen from the atmosphere to your blood
I have 24 keys but cannot open any locks. Sometimes loud, sometimes soft. What am I?
A little house full of meat, no door to go in and eat.
What am I?
Animal
Difficult
Easy
Food
Funny
Kids
Logic