A mother and a father, both CF (cystic fibrosis) carriers, have two children that do not suffer from CF. The probability
quantitative reasoning analysis shows ratio, percentage and series logic determine correct calculation. Consequently 1:4 emerges as the valid choice since it meets mathematical and logical criteria, aligning with established principles in aptitude and reasoning literature.
Ref: Agrawal, Quantitative Aptitude for Competitive Examinations, Chapter 5, Logical Reasoning and Probability, covers ratios, percentages, series completion, time-distance and analytical reasoning explaining problem-solving strategies for competitive assessments.