[单选题]
The graph shows the variation of the tmai44htlc x.0h*qjn/ otal electric potential due to two point ztpg kh:8dh)* eg:*h)z td k8phlectric charges $q_1$ and $q_2$ located 4.0m apart. The distance r is defined to be zero at the location of $q_1$.
What is the ratio of $\frac{q_1}{q_2}$
