[
  "Let boys = B, then girls = B + 5. Total pupils = B + (B + 5) = 35.",
  "2B + 5 = 35, so 2B = 30 and B = 15. Girls = 15 + 5 = 20. Ratio girls : total = 20 : 35.",
  "Simplify 20 : 35 by dividing by 5: 20 / 5 = 4, 35 / 5 = 7. Answer: 4 : 7 (option C)."
]