Data Sufficiency Advanced Strategies

Data Sufficiency questions have a fixed answer structure: (A) Statement 1 alone is sufficient; (B) Statement 2 alone is sufficient; (C) Both together are sufficient; (D) Each alone is sufficient; (E) Neither together is sufficient. The correct process is always to evaluate Statement 1 alone, then Statement 2 alone, then combined only if necessary. Never let information from one statement contaminate your evaluation of the other. The critical distinction is between value sufficiency and yes/no sufficiency. If the question asks 'What is x?', you need a single unique value. If it asks 'Is x > 5?', you need a definitive yes or no — not 'sometimes yes, sometimes no.'