A student conducted an experiment to test whether talking to plants would help them to grow faster. He set up the following two groups: Group 1: spoken to and hand watered
Group 2: not spoken to and watered with sprinklers

After three weeks, the plants in Group 1 showed much more growth than those in Group 2. Based on the results of this experiment, which is the best conclusion?
They are valid because the student ran a controlled experiment.
They are not valid because the student did not control all the variables that can affect plant growth.
They are valid because the dependent variable caused a change in the independent variable.
They are not valid because the time frame to grow a plant is too short.