Real depression cannot be as easily overcome as

The first remedy for the disease dates as back
as to 300 years ago even though ............... 
A) it was historically recordable as important for the
disease 
B) reliable drugs were not discovered until after 1943
C) only the bark of a North American tree was the
solution 
D) it was venomous and unsafe to use as tolerably as
those drugs used now 
E) doctors had also been totally successful in treating
the disease before 
Short Advanced Reading Comprehension Test 19 With MCQs and Answers 
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21. Doctors began treating malaria long before they
knew what caused it. The first recorded breakthrough
came in the 17th century when European
missionaries learned that the bark of South-
American cinchona trees contained the potent but
toxic remedy now known as quinine. By the time
pharmaceutical companies developed reliable
supplies, in the 1920s, a better treatment was
imminent. Chloroquine, introduced in 1943 by the
U.S. Military, was as potent as quinine -yet it was
longer active, cheaper to produce and so well-
tolerated that people no longer had to wait passively
for malaria to strike. They could take regular doses in
order to prevent the disease.
Chloroquine is different from quinine in that
......................... 
A) it was developed by the military during a war 
B) it was twice as potent as quinine although it had
certain weaknesses 
C) it could be taken to prevent the disease as well as
to cure it after infection