Answer:
b. Constant magnitude, but varying direction, perpendicular to the equipotential.
Explanation:
As we know that the relation between electric field and electric potential is given as

here if we say that potential is constant because electric field sensor is moving along equi-potential line.
Then we will say
V = constant
so we have

so electric field will remain constant always in magnitude and always remains perpendicular to the surface
so we have
b. Constant magnitude, but varying direction, perpendicular to the equipotential.
Normal Force = 54 N
acceleration = 1.2 m/s^2
For Normal Force:
According to the force diagram, we can come up with the equation (all up and down forces):
10 sin 30 + Normal Force - 58.8 = 0
Normal Force = 53.8 N = 54 N
For acceleration:
According to the force diagram, we can come up with the equation (all left and right forces):
10 cos 30 - 1.5 = (6.0) (Acceleration)
Acceleration = 1.19 m/s^2 = 1.2 m/s^2