Which type of gas is needed for plants to make their own food?
A.hydrogen
B.nitrogen
C.carbon dioxide
D.oxygen

D. carbon dioxide

Explanation:

Plants need CARBON DIOXIDE and water to produce oxygen and glucose.

Explanation:

An independent variable is a variable that represents a quantity that is being manipulated in an experiment

In the given conditions, three pieces of ice are covered with either tinfoil, plastic wrap or paper and fourth piece is left uncovered so it is clearly visible cover material is being changed for different ice piece hence independent variable is the type of cover material

A dependent variable represents a quantity whose value depends on how the independent variable is manipulated

In the given conditions, final mass of each piece of ice is calculated where three pieces of ice are covered and one is left uncovered therefore the final mass of ice piece is dependent on the type of cover material hence dependent variable is mass of the ice