P1: Everyone who has graduated from TopNotch High School has an intelligence quotient (IQ) of over 120.
P2: Most students with an IQ of over 120 who apply to one or more Ivy League universities are accepted by at least one of them.
P3: All students with an IQ of over 150 who apply to one or more Ivy League universities are accepted by at least one of them.
From the first premise we know that every graduate from TopNotch has an IQ of over 120. The second sentence has two parts so I broke it up into two premises for clarity. P2 states that most students with an IQ greater than 120 are accepted by at least one of the Ivy League schools they apply. P3 states that all students with an IQ greater than 150 are accepted by at least one of the Ivy League schools they apply.
The question stem is asking for the conclusion that is best supported by the above facts.
A)"Every graduate of TopNotch High School with an IQ of 150 has been accepted by at least one Ivy-League university." Incorrect. This is incorrect because it refers to every graduate with an IQ of 150. The premise P3 states that "all students with an IQ of over 150 who apply to one or more Ivy League universities are accepted by at least one of them". If a student has an IQ of exactly 150 then he is characterized by the premise P2, "Most students with an IQ of over 120 who apply to one or more Ivy League universities are accepted by at least one of them". This premise leaves open the possibility that some students with an IQ over 120 but less than or equal to 150 are not accepted. In other words, it is possible for a student to have an IQ of exactly 150 and not be accepted by an Ivy League school.
Even if this answer choice referred to graduates with IQs over 150, it would still be wrong. It would be wrong because the premises do not state that every graduate applies to an Ivy League school. Therefore, it is possible for a student to have an IQ over 150 and not be accepted to an Ivy League school simply because he did not apply to one.
B) "If a person is a high-school graduate and has an IQ of less than 100, he or she could not have been a student at TopNotch High School." Incorrect. This answer is incorrect because it confuses students and graduates. The first premise states that every graduate of TopNotch has an IQ over 120. This answer choice references a high-school graduate. We don't know where they graduated from. It is possible that someone attended TopNotch and then moved and graduated from a different school. In this case it would be possible for a high-school graduate to have an IQ of less than 100 and have attended TopNotch.
C) "If a person has an IQ of 130 and is attending an Ivy-League university, it is possible for him or her to have graduated from TopNotch High School." Correct. This answer is correct because it does not violate any of the premises. The answer choice states that if a student has an IQ of 130 and is attending an Ivy League school that student may have graduated from TopNotch. From the premises we know that all graduates from TopNotch have an IQ over 120 and that most of these students will get into one or more Ivy League schools they apply. It follows that if a person has an IQ of 130 and is attending an Ivy-League university, they may have graduated from TopNotch. This is exactly what the answer choice states.
D) "At least one graduate from TopNotch high school who has applied to at least one Ivy-League university has been accepted to one of them." Incorrect. This answer choice states that at least one graduate from TopNotch that applies to an Ivy League school will get in. This answer choice is incorrect because it is possible that NO graduates from TopNotch are admitted to Ivy League schools. The second and third premises leave open the possibility that a person that has an IQ over 120 and less than or equal to 150 may not be accepted. If in a given year, only students that fall into this category (120 < IQ <= 150) apply to Ivy League schools, it is possible that none of them get in.
E) "If a high-school graduate has an IQ of 150 and is not attending an Ivy-League university, then he or she did not apply to one of them." Incorrect. This answer choice state that if someone has a IQ of 150 and they are not attending an Ivy League school, then they did not apply. This answer is incorrect for reasons similar to answer (A). The premise refers to people with IQs over 150. It is possible for someone that has an IQ of exactly 150 to apply to an Ivy League school and be denied.
Additionally, this answer is wrong because it is possible for someone to attend an non-Ivy League school after applying and getting admitted to an Ivy League school. In other words, not everyone that is accepted to an Ivy League school chooses to attend.