Consider the three masses shown, $M_1,M_2,$ and $M_3.($Note the diagram is not to scale.$)$ It is known that $M_3=4M_1.$ If the distance between $M_1$ and $M_2$ is $R_1,$ the distance between $M_2$ and $M_3$ is $R_2,$ and the magnitude of the force of gravity between $M_1$ and $M_2$ is the same as the magnitude of the force of gravity between $M_2$ and $M_3,$ which of the following must be true?

A$.R_2=2R_1$

B$.R_2=\frac{1}{2}{R}_1$

C$.R_2=4R_1$

D$.$ We could not know any of the above without knowing the mass of $M_2.$