Question

student conducts an experiment to grow tomato plants and collects the following data.

fertilizer used	height after 60 days (in cm)	number of seeds planted	size of pot (in cm)
fertilizer b	31.75	5	15
fertilizer c	35.56	5	15

if the student decides to add a control to the experiment, which of the following should they do?
a measure the number of leaves in addition to the height of the plant.
b grow at least three plants with each type of fertilizer.
c add a plant that receives no fertilizer.
d measure the height of the plants more frequently.

Explanation:

In an experiment, a control group is used to compare with the experimental groups. Here, the experiment is about different fertilizers (A, B, C). A control would be a group with the same conditions (pot size, seeds planted) but no fertilizer. Option C suggests adding a plant with no fertilizer, which serves as the control to see the effect of no fertilizer compared to the ones with fertilizers. Option A is adding a new measurement, B is increasing sample size, D is changing measurement frequency, none of which are about creating a control.

Answer:

C. Add a plant that receives no fertilizer