Answer:
A the distance between the positive charge and the electron
B the charge on the electron
D the charge of the positive charge
Step-by-step explanation:
The electric field produced by the positive charge Q at the location of the electron is given by

where
k is the Coulomb constant
Q is the charge
r is the distance between the charge Q and the electron
The force exerted on a charged particle by an electric field is given by

where q is the magnitude of the charged particle. So, the force exerted on the electron in this problem is

where e is the charge of the electron. As we see from the equation, the force depends only the following quantities:
A the distance between the positive charge and the electron (r)
B the charge on the electron (e)
D the charge of the positive charge (Q)