Help me with a science problem plz?

Question

A student wanted to determine the effect that certain soil mixtures would have on the growth rate of pea plants. He selected 3 groups of idenetical pea plants. He gave all groups the same amount of light, water, and grew them at the same temperature. However he grew group 1 in plain soil. Group 2 in soil plus substance x and group 3 in soil with substance x &y. At the end of two weeks he recorded the growth in centimeter.

group 1 - grew 1cm

group 2 - grew 3 cm

group 3- grew 5cm

a. what group(s) served as the control?

b. what group(s) served as the variable

c. what was the independent variable

what was the dependent variable

what were the controlled variables

omgg hellllp plzzzzzzzzzzzzz

Answer 1

a.  both group 1 and 2 served as controls

Group 1 served as a control for plant growth in the absence of the two substances whiel Group 2 served as a control for plant growth in the absence of substance y.

b.  both group 2 and 3 served as variables

Group 2 served as the variable for the effects of substance x while Group 3 served as the variable for the effects of substance x + y.

c.  independent variable = time

dependent variable = growth

controlled variables = light, water, temperature