Sure, let's look at the rules. This is a hybrid game that requires us to match witnesses to prosecutors and determine the order of interviews over exactly four days. We have four witnesses - F G H I, each interviewed by one of three investigators - Q R S. Each investigator interviews at least one witness and each witness is interviewed by exactly one investigator. This tells us that 3 investigators interview 1 witness and 2 investigator interviews 2 - 2-1-1.
W: __ __ __ __ I: __ __ __ __ 1 2 3 4
The interview is governed by the following rules: (1) G and H must be interviewed by the same investigator. This rule tells us that whoever interviews G & H is the only investigator that interviews two witnesses, the rest of them interview one witness each - F and I.
(3) G and I cannot be interviewed on consecutive days.
(4) Q must interview F. Q =F This rule allows us to infer that either R or S must interview G & H.
(5) R must conduct the third interview.
W: __ __ __ __ I: __ __ R __ 1 2 3 4
The question asks us if R interviews I, which of the following must be true?
Let's put this condition on our diagram:
W: __ __ I __ I: __ __ R __ 1 2 3 4
Since G and I cannot be interviewed on consecutive days per rule (3), we know that G must be interviewed on day 1.
W: G __ I __ I: __ __ R __ 1 2 3 4
We can thus conclude that (B) must be true.
Let's briefly look at the rest of the answer choices. We can eliminate (A) and (E) because G must be first and I must be third. We can eliminate (C) and (D) because H could be either second or fourth, thus it is not true that it must always be second or always be fourth in every scenario as the correct answer to a must be true question requires.
W: G H I F I: S S R Q 1 2 3 4
W: G F I H I: S Q R S 1 2 3 4
Let me know if this makes sense and if you have any other questions.
