Answer:
The correct option is (b). The treatment variable is riding a bike to school. The outcome variable is the child's attention span.
Explanation:
Consider the provided information.
Independent Variable (Treatment Variable): The variable which can be manipulated or changed by researchers, not by other variables in the experiment.
So here riding a bike to school is the Treatment variable because this can be manipulated by ht e researchers.
Outcome variables: The outcome variables are dependent on the independent variables.
Here, attention span is depending on the treatment variable.
Therefore, the correct option is (b). The treatment variable is riding a bike to school. The outcome variable is the child's attention span.