In 1998, more citizens from the country of Monrovia migrated from Monrovia to neighboring Abstania than during any prior year. In 1998, the number of reported violent crimes in Abstania increased dramatically over 1997. The unavoidable conclusion is that Monrovians who migrated from Monrovia to Abstania were responsible for this increase.

Which of the following statements, if true, would most seriously weaken the claim that Monrovians were responsible for the increase in violent crime in Abstania during 1998?
(A) Each year more violent criminals are apprehended in Abstania than in Monrovia.
(B) During 1998 more violent crimes were reported in Abstania than in Monrovia.
(C) In 1998 no Monrovians migrated from either Monrovia or Abstania to any country other than Monrovia or Abstania.
(D) In 1998 the number of unreported violent crimes in Abstania increased as well.
(E) In 1998 fewer Monrovians migrated from Monrovia to Abstania than from Abstania to Monrovia

E

In 1998, more citizens from the country of Monrovia migrated from Monrovia to neighboring Abstania than during any prior year. In 1998, the number of reported violent crimes in Abstania increased dramatically over 1997. The unavoidable conclusion is that Monrovians who migrated from Monrovia to Abstania were responsible for this increase.

the first assumption: there was no other reason that was responsible for increase of reported violent crimes.
the second assumption: the number of Monrovians in Abstania increased in 1998.
the third assumption: the ratio of reported violent crimes to unreported ones is the same during all period.

Which of the following statements, if true, would most seriously weaken the claim that Monrovians were responsible for the increase in violent crime in Abstania during 1998?

(A) Each year more violent criminals are apprehended in Abstania than in Monrovia. - irrelevant. we don't know populations of both countries to calculate ratio and to say that Monrovians are more criminal than citizens of Abstania
(B) During 1998 more violent crimes were reported in Abstania than in Monrovia. - irrelevant. there is no information about population of counties to make a right comparison
(C) In 1998 no Monrovians migrated from either Monrovia or Abstania to any country other than Monrovia or Abstania. - irrelevant.
(D) In 1998 the number of unreported violent crimes in Abstania increased as well. - irrelevant. Slightly strength arguments (the third assumption)
(E) In 1998 fewer Monrovians migrated from Monrovia to Abstania than from Abstania to Monrovia - ok. it destroys the second assumption.
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The correct response is (E). The argument relies on the unstated assumption that Abstania's Monrovian population either remained stable or increased during 1998. However, (E) provides that this population actually declined in 1998, despite the influx of Monrovians. Given that the number of Monrovians residing in Abstania decreased while the crime rate increased, (E) reduces the likelihood that it was Monrovians who were responsible for the increase in violent crime in 1998.

(A) would appear to weaken the argument, by providing ostensible evidence that Abstanians are more likely than Monrovians to commit violent crimes. However, (A) does not account for the possibility that in Monrovia far more violent criminals go unapprehended than in Abstania. In fact, the argument's explicit reference to "reported" violent crimes underscores this possibility, which prohibits us from drawing any firm conclusion as to which group is more likely responsible for violent crimes.

(B) provides no information useful in evaluating the argument. Whether (B) strengthens the argument depends on addition considerations as well, such as: the total population of Monrovia compared to Abstania; whether the Monrovian population increased or decreased in each country during the year; and whether the crime rate in Monrovia increased or decreased during 1998.

(C) actually strengthens the argument. By providing evidence that number of Monrovians residing in Abstania increased in 1998, (B) makes it more likely that Monrovians were responsible for the increase in violent crime that year.

(D) actually strengthens the argument, by affirming the essential premise that the number of violent crimes in Monrovia increased dramatically during 1998.

(A) Each year more violent criminals are apprehended in Abstania than in Monrovia. [Argument is about crime in Monrovia – Eliminate it]
(B) During 1998 more violent crimes were reported in Abstania than in Monrovia. [Argument is about crimes in Monrovia – Eliminate it]
(C) In 1998 no Monrovians migrated from either Monrovia or Abstania to any country other than Monrovia or Abstania.[Where Monrovians migrated is irrelevant to the argument – Eliminate it]
(D) In 1998 the number of unreported violent crimes in Abstania increased as well. [This is irrelevant to the argument]
(E) In 1998 fewer Monrovians migrated from Monrovia to Abstania than from Abstania to Monrovia [Hold it]

Answer: E