Answer:
C. identifying the problem
Step-by-step explanation:
To be sure of what the experiment involves one need to have an hypothesis to guide the task.
Assuming the hypothesis in the experiment is , “changing the amount of weight at the end of the pendulum will change the period of the pendulum.”
The experiment design would be complementary in that it would entail measuring the period with just one amount of weight, then changing the weight without changing any other variables, then measuring the period with the new amount of weight.
Changing the pendulum design after the first trial was an example of identifying the problem or the variable tied to the one factor that we are solving for.