Option 1 -> States that (A) and (D) are correct. However, (D) is incorrect because when elasticity < 1 (inelastic demand), MR is negative, not positive.
Option 2 -> States that (A) and (B) are correct. However, (B) is incorrect because when elasticity > 1 (elastic demand), MR is positive, not negative.
Option 3 -> States that (B) and (D) are correct. Both statements are incorrect as explained above.
Option 4 -> States that (A) and (C) are correct, which accurately reflects the relationship between MR and price elasticity.
Hence, Option 4: (A) and (C) only -> The relationship between MR and price elasticity is given by MR = P(1 - 1/|Ed|). When |Ed| < 1 (inelastic), 1/|Ed| > 1, making (1 - 1/|Ed|) negative, thus MR < 0 (statement A is correct). When |Ed| > 1 (elastic), 1/|Ed| < 1, making (1 - 1/|Ed|) positive, thus MR > 0 (statement C is correct). When |Ed| = 1 (unit elastic), MR = 0. Therefore, statements (A) and (C) correctly explain the relationship. -> correct