Student experiment comparing plant growth under different light brightness levels.

Let’s look at the two pictures carefully.

In both pictures, we see:
- A plant in a pot
- A light shining down on it
- A thermometer on the wall

But there’s one big difference between the two pictures:

→ In the left picture, the light is shining straight down (like from directly above).
→ In the right picture, the light is shining at an angle — it’s tilted to the side.

That means the student changed how the light hits the plant — specifically, the angle of the light.

Now let’s check the answer choices for question 1:

a. the angle of the light shining on the plant → ✔ This matches what we saw!
b. the type of soil → We can’t even see the soil, and both pots look the same.
c. the brightness of the light → The lights look equally bright in both pictures.
d. the temperature → The thermometers show the same level in both pictures.

So the change variable (also called the independent variable) is the angle of the light.

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For question 2: What are the control variables? These are things the student kept the SAME in both setups so they don’t mess up the experiment.

Looking at both pictures, these things are identical:

- The kind of plant (same size, same leaves)
- The pot (same shape and color)
- The light source (looks like the same lamp)
- The brightness of the light (no dimmer or brighter)
- The thermometer reading (same temperature shown)
- The background / room setup (same walls, same position)

So the student made sure everything except the angle of the light stayed the same.

Final Answer:
1. a. the angle of the light shining on the plant
2. The control variables are: the type of plant, the pot, the light source, the brightness of the light, the temperature (as shown by the thermometer), and the overall setup/environment.