How has the relative importance of each item's dollar value changed?

In which research method does a researcher change the value of one variable to determine how the change affects another variable? a. experiment b. observational research c. survey d. case study

This cartoon appeared in 1916. the topic of the cartoon isa)the reason for the start of world war i.b)the success of us submarines in world war i.c)the military alliance between germany and mexico.d)the attitude in the us towards submarine warfare in world 

Explain what might happen if the supreme court did not have the power to check the other two branches.