DNA complementary base pairing Steps: - Strand 1 total: 29 (A) + V (C) + 14 (G) + W (T) = 73, so V + W = 30. - Strand 2 A = 21 pairs with strand 1 T, so W = 21 and V = 9. - Strand 2 C (X) pairs with strand 1 G = 14, so X = 14; strand 2 G (Y) pairs with strand 1 C = 9, so Y = 9. - Strand 2 T (Z) pairs with strand 1 A = 29, so Z = 29; thus V W X Y Z = 9 21 14 9 29. Why A is correct: - Matches Chargaff's rules where A pairs with T (29=29, 21=21) and C pairs with G (9=9, 14=14), with totals summing to 73 per strand. Why the others are wrong: - B: Fails to satisfy base pairing equality (e.g., A ≠ T counts). - C: V + W = 30 but Z = 14 ≠ A1 = 29, violating A-T pairing. - D: V + W = 38 > 30, …