Frank needs to move a box by sliding it across the floor. Which two factors will most strongly affect how hard Frank needs to push the box?
OPTIONS:
- The density of the box material and the hardness of the floor
- The thickness of the box material and the hardness of the floor
- The total mass of the box and the friction between the box and the floor
- The total height of the box and the distance between his hands and the floor

The total mass of the box and the friction between the box and the floor


Which of these best defines communicable diseases?
OPTIONS:
- They can be cured.
- They are caused by bacteria.
- They are spread to others.
- They can spread only in winter.

They are spread to others.


Which action forms a different chemical substance?
OPTIONS:
- crushing a rock
- burning a piece of wood
- mixing salt and pepper
- melting an ice cube


burning a piece of wood