Akela wrote:
In polluted industrial English cities during the Industrial Revolution, two plant diseases—black spot, which infects roses, and tar spot, which infects sycamore trees—disappeared. It is likely that air pollution eradicated these diseases.
Which one of the following, if true, most strengthens the reasoning above?
(A) Scientists theorize that some plants can develop a resistance to air pollution.
(B) Certain measures help prevent infection by black spot and tar spot, but once infection occurs, it is very difficult to eliminate.
(C) For many plant species, scientists have not determined the effects of air pollution.
(D) Black spot and tar spot returned when the air in the cities became less polluted.
(E) Black spot and tar spot were the only plant diseases that disappeared in any English cities during the Industrial Revolution.
Source: LSAT
+1 for D(A) Scientists theorize that some plants can develop a resistance to air pollution.
-Incorrect. This is a Weakener, if plants develop resistance to ar pollution then why would they get eradicated due to air pollution.(B) Certain measures help prevent infection by black spot and tar spot, but once infection occurs, it is very difficult to eliminate.
-Incorrect. Certain measures? What measures? This statement is inconsistent.(C) For many plant species, scientists have not determined the effects of air pollution.
-Incorrect. This statement is irrelevant(D) Black spot and tar spot returned when the air in the cities became less polluted.
-Correct. This statement tell us that both the diseases returned when air pollution reduced. This gives us a relation between air pollution and diseases. (E) Black spot and tar spot were the only plant diseases that disappeared in any English cities during the Industrial Revolution.
-Incorrect. This statement doesn't give us any information which would strengthen the fact that diseases were eradicated due to air pollution