Jamal is testing muscle strength in frogs. He thinks that their muscle strength will increase if more protein is added to the frogs’ diet. To test this, he increases the protein in twenty frogs’ diet. He leaves the other twenty frogs’ diet as is. Jamal then places the frogs on a line and measures the distance they can jump. He performs the experiment every day at the same time using the same measuring stick.

What represents the control group?
1 the frogs that did not get the extra protein
2 the frogs that got the added protein
3 Jamal’s use of the same measuring stick
4 Jamal’s use of twenty frogs in each group