Carie and Heather wanted to know if the size of a coin will affect the number of drops of water it can hold. So they used a dropper to place water on a quarter, nickel, and penny.
What is the independent variable?
number of drops of water
O type of liquid
O size of the dropper
O size of the coin

The independent variable is the size of the coin.

Explanation:

The independent variable is the variable that changes, and it's also the variable that the dependent variable depends on. So depending on the size of the coin,  results in the number of drops of water the coin could hold.

Therefore the independent variable is the size of the coin.

the answer is:

carbon dioxide