Use the table below to answer the question.

a student wants to test the hypothesis that fertilizer improves the growth rate of grass seeds. to test this hypothesis, the student put the same amount of grass seed in 3 containers with the same type of soil. the student measured the growth at the end of the week. all plants received equal amounts of water and sunlight.

a: 2cm

b: 4cm

c: 6cm

d: 12cm

what is the mean height for the grass used as a control?