Why are the rocks and pebbles found on riverbeds usually smooth?
A: The rocks and pebbles rub against each other as water flows over them.

A statue and a table are both made of the same type of marble. Which of the following properties will most likely be the same for both of these objects?
A: hardness

If a child scrapes his foot on a piece of rusty metal, it is important to get medical treatment because the
A: metal may be contaminated and cause infection.

Which of the following is a similarity 20 between x-ray waves and sound waves?
A:
Both transfer energy.