Question

dent 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. The control group should have the same conditions as the experimental groups except for the independent variable (here, the type of fertilizer). So, adding a plant that receives no fertilizer (the independent variable is absent) serves as a control to see the effect of the fertilizers. Option A is about adding a new measurement, B is about sample size (already 5 plants), D is about measuring height more often (not related to control). So the correct action for a control is option C.

Answer:

C. Add a plant that receives no fertilizer