Answer:
Beatrice could change the independent variable
Explanation:
Beatrice wants to assess the influence of a lift's movement on her body weight. In this experiment, we can say that Beatrice's independent variable is the movement of the elevator, while the dependent variable is her body weight.
As you may already know, the independent variable is the one that can be measured and that influences a result to happen, while the dependent variable is the one that is influenced for a result to happen.
If Beatrice modified the independent variable, she could have a better result in her experiment. This is because the "elevator movement" is a very vague concept which leaves your experiment imprecise, since this variable cannot be quantified. It could then change this variable to "the elevator's speed" or "the elevator's rise and fall time".