Felipe and marahea where studying friction they did a experiment and placed four blocks on a plastic tray which block will have the least amount of friction a a ice block, b a sponge block, c sandpaper block, or d a plastic block

Well just imagine if you took these items and rubbed them together.
 I will give you two answers to cross out and you will have to figure out the rest.
 Plastic - Imagine you were rubbing two candy wrapper together would you have a really hard time? No you would just make a lot of noise.
Sponges- Sponges are really hard and smooth when they are not in the sink. They would have no problem rubbing against each other. 

Think about which materials would be most difficult to rub together.