The golden toad of Costa Rica, whose beauty and rarity inspired an unusual degree of human interest from a public generally unconcerned about amphibians, may have been driven to extinction by human activity nevertheless. In the United States, a public relations campaign featuring the toad raised money to purchase and protect the toad’s habitat in Costa Rica, establishing the Monteverde Cloud Forest Preserve in 1972. Although this action seemed to secure the toad's future, it is now apparent that setting aside habitat was not enough to save this beautiful creature. The toad's demise in the late 1980s was a harbinger of further species extinction in Costa Rica. Since that time, another twenty of the fifty species of frogs and toads known to once inhabit a 30 square kilometer area near Monteverde have disappeared.
The unexplained, relatively sudden disappearance of amphibians in Costa Rica is not a unique story. Populations of frogs, toads, and salamanders have declined or disappeared the world over. Scientists hypothesize that the more subtle effects of human activities on the world's ecosystems, such as the build-up of pollutants, the decrease in atmospheric ozone, and changing weather patterns due to global warming, are beginning to take their toll. Perhaps amphibians - whose permeable skin makes them sensitive to environmental changes - are the "canary in the coal mine," giving us early notification of the deterioration of our environment. If amphibians are the biological harbingers of environmental problems, humans would be wise to heed their warning.


q : It can be inferred from the passage that
A. only thirty species of frogs and toads remain in Costa Rica
B. humans do not have permeable skin
C. the build-up of pollutants in the atmosphere causes a decrease in atmospheric ozone
D. humans do not usually take signals of environmental deterioration seriously
E. Costa Rica suffers from more serious environmental problems than many other countries


WHY D IS WRONG ?

WHY D IS WRONG ?[/quote]

this is an inference problem. on inference problems, you MUST pick a statement that HAS TO BE TRUE based on the statements in the passage.

in other words, you have to ignore what "inference" usually means in real life. when most normal people say "infer", they mean that you should generalize, make assumptions, and try to broaden the scope of your observations. you are not allowed to do any of those things here ... at all.

--

why did you think (d) is true?
this passage contains no information from which we can draw any deductive conclusions about how seriously humans take signals of environmental deterioration.

what's the OA?Is it A?

"Since that time, another twenty of the fifty species of frogs and toads known to once inhabit "

Be careful! Look at what the passage says:
"Since that time, another twenty of the fifty species of frogs and toads known to once inhabit a 30 square kilometer area near Monteverde have disappeared."

So there are only 30 species known to inhabit a particular AREA, NOT the country of Costa Rica! A is not right.

Try to narrow down and see what answer must be true.

_________________
Jamie Nelson
ManhattanGMAT Instructor