The correct answer is: C. Both A and B.
An elastic demand curve is a curve that is relatively flat, meaning that a small change in price will lead to a large change in quantity demanded. A perfectly inelastic demand curve is a curve that is vertical, meaning that quantity demanded will not change at all regardless of the price.
Option A is incorrect because an elastic demand curve is not necessarily shown by a letter “D” demand curve. A letter “D” demand curve can be either elastic or inelastic, depending on the slope of the curve.
Option B is incorrect because a perfectly inelastic demand curve will not be a horizontal straight line. A perfectly inelastic demand curve will be a vertical line.
Therefore, both options A and B are incorrect.