y = 32x is a proportional relationship. it has a constant ratio and passes through the origin--remember that the base equation, straight through the origin (0, 0), is y = x.
your other answer choices do not pass through the origin. choice 2 can be changed to read y = x + 4. an equation with a y-intercept 4 does not cross through the origin; the y-intercept must be 0 to pass through the origin. choice 3 has another y-intercept that isn't 0.