Distribution characteristics of point charge electric field lines; The electric field lines of positive charge electric field start from positive charge and end at infinity, and those of negative charge electric field start from infinity and end at negative charge.

The direction of electric field intensity generated by two points between A, A and B is all to the left, and the resultant field intensity cannot be zero. So, A is wrong.

On the right side of B and A, the electric field intensity generated by A is to the right, the electric field intensity generated by B is to the left, and the electric field intensity is in the opposite direction. Moreover, the power of question A is larger than that of question B, and question A is closer. From the formula of point charge field strength E=kqr2, it can be seen that the electric field strength at the same point cannot be equal, so the combined electric field strength cannot be zero. So, B is wrong.

C on the left side of b, the electric field intensity generated by a is to the left, the electric field intensity generated by b is to the right, and the electric field intensity direction is opposite. However, because the electric quantity of A is greater than that of B, and A is far away, it can be seen from the formula of point charge field strength E=kqr2 that the electric field strength at the same point may be equal, so the combined electric field strength may be zero. So, C is correct.

D, it can be seen from the above that D is wrong.

So choose: C.