Explanation:

Option (2) is correct.
Explanation: Geometric method was suggested by Prof. Marshall and is used to measure the elasticity at a point on the demand curve.
(i) When there are infinitely small changes in price and demand, then the 'Geometric Method' is used.
(ii) This method is also known as 'Graphic Method' or 'Point Method' or 'Arc Method'. Elasticity of demand (Ed) is different at different points on the same straight line demand curve.
(iii) In order to measure Ed at any particular point, lower portion of the curve from that point is divided by the upper portion of the curve from the same point.