Question

Which one among the following must have two sources?

• A. A
• B. B
• C. C
• D. D
• A. 2
• B. 3
• C. 4
• D. 5
• A. F
• B. B
• C. I
• D. None of the nine
• A. C introduced the wrong answer to question
• B. E introduced the wrong answer to question
• C. F introduced the wrong answer to question
• D. H introduced the wrong answer to question

Answer 1

The Correct Option is B

Step 1: Each person copies answers from their sources only if both sources provide identical answers; otherwise, the answer is left blank. The number of blank answers for a person indicates the number of questions where their sources provided different answers.
Step 2: A person with two sources will have blank answers when the sources disagree. The table shows B has 46 blank answers, suggesting a high likelihood of two sources, as a single source would imply fewer discrepancies.
Step 3: Compare the blank answers: A (26), B (46), C (17, 46, 60), D (27), E (27, 50), F (27), G (27), H (none listed), I (17, 26, 50). B’s 46 blank answers are significantly higher, indicating two sources providing different answers frequently.
Step 4: Since the mastermind has the correct key and others copy from sources, B’s high blank count suggests reliance on two sources with conflicting answers. Other options (A, C, D) have lower or ambiguous blank counts, making B the most likely to have exactly two sources.

Answer 2

Step 1: C’s answer key depends on their sources. Each person’s key is derived from their sources’ keys, and the process forms a dependency chain.
Step 2: From the table, C has 27 or 26 wrong answers and 17, 46, or 60 blank answers. The high blank counts suggest C has two sources, as blanks occur when sources disagree.
Step 3: Assume C’s sources are two people (not the mastermind) who have already prepared their keys. If each source has one source (forming a chain), the minimum number of people before C is two (C’s two sources).
Step 4: Since the mastermind’s key is correct and not counted, the minimum number of people (excluding the mastermind) needed before C is 2, assuming a simple dependency where C’s sources are directly linked to the mastermind or others with prepared keys.
Step 5: Higher options (3, 4, 5) imply longer chains, but the question asks for the minimum, making 2 sufficient.

Answer 3

Step 1: For G and H to be sources to a person, that person must have a number of blank answers equal to or less than the sum of wrong answers from G and H, as blanks occur when sources disagree.
Step 2: G has 25 wrong answers and 27 blank answers; H has 46 or 52 wrong answers and no blank answers listed. Assume H has 46 wrong answers for simplicity.
Step 3: Check each option:
- F has 27 blank answers, but G (25 wrong) and H (46 wrong) could produce up to 25 blanks (if G’s wrong answers are a subset of H’s). This is close but not definitive.
- B has 46 blank answers, which exceeds G’s 25 wrong answers, making it impossible for G and H to be sources (blanks cannot exceed source errors).
- I has 17, 26, or 50 blank answers. The 17 or 26 blanks are possible, but 50 exceeds G’s 25 wrong answers.
- None of the nine: If no single person’s blank answers consistently match G and H as sources, this is likely.
Step 4: Since B’s high blank count and I’s variable counts make them unlikely, and F’s dependency is not confirmed, “None of the nine” fits if G and H’s errors don’t align with any person’s blanks.
Step 5: The investigative agency’s data and lack of clear source matches suggest no single person relied on both G and H.

Answer 4

Step 1: Wrong answers in a person’s key come from copying incorrect answers from their sources or introducing new errors if they have no sources.
Step 2: Check E’s data: E has 46 or 50 wrong answers and 27 or 50 blank answers. The presence of 46 in wrong answers suggests E may have introduced or copied a wrong answer for question 46.
Step 3: Compare options:
- (A) C has 27 or 26 wrong answers, possibly including question 27, but no specific evidence confirms C introduced it.
- (B) E’s wrong answers include 46, and since E could have introduced errors (especially if they have fewer sources), this is plausible.
- (C) F has 27 wrong answers, but no mention of question 54, making this unlikely.
- (D) H has 46 or 52 wrong answers, including 46, but no evidence confirms H introduced it.
Step 4: Since E’s wrong answers explicitly include question 46, and the question asks for a true statement, option (B) is supported by the data.
Step 5: Verify: No other option has direct evidence linking the person to the specific question number as clearly as E to question 46.