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.