How can a scalar field be represented graphically?

A scalar field can be represented by its level surfaces, that is, by joining with a line all the points that have the same potential.
The density of the lines in a scalar field is proportional to the intensity of the field.
The gradient of a scalar field is responsible for the variation of potential in each point.
a) Only the first statement is correct.
b) Only the second statement is correct.
c) Only the third statement is correct.
d) All statements are correct.