What do the electric force lines indicate?

I- The direction and sense in which a positive test charge would move if placed in an electric field.
II- The direction and sense in which a negative test charge would move if placed in an electric field.
III- The direction and sense in which a neutral test charge would move if placed in an electric field.
IV- The intensity of the electric field at each point.
a) I and II are correct.
b) I, II, and IV are correct.
c) II and IV are correct.
d) I, II, III, and IV are correct.