What type of data is recorded by the electrocardiogram? A.
the sound of the heart beating
B.
the amount of oxygen in the blood
C.
the electrical activity of the heart
D.
the force from the heart beating

Ruby is conducting an investigation. an advantage of her design is that she can use a large range of variables, with that she can not be sure that one variable is the cause of another. what kind of investigation is ruby most likely conducting?