Question

which variable is carefully and originally changed or adjusted by the investigator in a controlled manner?
dependent variable
independent variable
controlled variable
hypothetical variable

Explanation:

In an experiment, the independent variable is the one that the investigator manipulates or changes in a controlled way to observe its effect on the dependent variable. The dependent variable changes in response to the independent variable. Controlled variables are kept constant to ensure that only the independent - variable affects the dependent variable. Hypothetical variables are not real variables in the context of experimental design.

Answer:

B. independent variable