IMO D

E only mentions that they were susceptible and not actual contraction of infections caused by the debris

Some scientists believe that 65 million years ago an asteroid struck what is now the Yucatan Peninsula, thereby causing extinction of the dinosaurs. These scientists have established that such a strike could have hurled enough debris into the atmosphere to block sunlight and cool the atmosphere. Without adequate sunlight, food sources for herbivorous dinosaurs would have disappeared, and no dinosaurs could have survived a prolonged period of low temperatures. These same scientists, however, have also established that most debris launched by the asteroid would have settled to the ground within six months, too soon for the plants to disappear or the dinosaurs to freeze.
Which one of the following, if true, most helps to resolve the apparent discrepancy between the scientists’ beliefs and the scientists’ results, as described above?
(A) Loss of the herbivorous dinosaurs would have deprived the carnivorous dinosaurs of their food source.
(B) Dinosaurs inhabited most landmasses on the planet but were not especially abundant in the area of the asteroid strike.
(C) A cloud of debris capable of diminishing sunlight by 20 percent would have cooled the earth’s surface by 7 to 10 degrees Celsius.
(D) The asteroid was at least 9.6 km in diameter, large enough for many dinosaurs to be killed by the strike itself and by subsequent tidal waves.
(E) Dinosaurs were susceptible to fatal respiratory problems cause by contamination of the air by asteroid debris.

E....

the paradox between the belief and the result is what needs to be resolved....

the belief is that the asteroid debris blocked sunlight resulting in a loss of vegetation and thereby extinction of dinosaurs.... and the result is that asteroid debris never blocked sunlight because the debris settled within six months of the collision event....

A. blocked sunlight and subsequent vegetation loss led to B. extinction (not true as explained in the argument)

which would mean that

A. (something else) led to B. extinction...

only E seems to offer an alternative explanation....

A. ok... but does not explain extinction.. only says the food chain got disrupted...
B. straightforward reject..
C. too many numbers (7 to 10 degree celsius) that are useless in explaining extinction
D. of course the asteroid may be large enough to kill "many" dinosaurs but does that necessarily mean extinction?
E. relates how the asteroid debris would have caused extinction.... asteroid debris -> air contamination -> "fatal" respiratory problems -> WIPEOUT....

+1 for E.
D is not correct because it states many dinosaurs and not all dinosaurs.

d) killing many dinosaurs isn't enough. why did all die then?
e) fatal respiratory problems for 6 months sounds like a valid reason for extinction.
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