Although I was little confused b/w A and E but my take is A
(A) If a species' resource requirement for maintaining its strength outweighs the resources available, that species will not survive - Correct.
Given that when Maintenance of strength < or = Resource available only then species survives.
Therefore, When Maintenance of strength > Resource available, then species won't survive.
(B) Strength does not provide a survival advantage for hunting food - Opposite to given in stem.
(C) The phrase "survival of the fittest" should not be used by the scientific community - Cannot be said or cannot be inferred or not mentioned
(D) The species with the least strength is the most likely to survive in a famine - Stem says that only species that survives whose requirement for maintaining its strength does not outweigh the resources available. Therefore, within the available resources, strength can be higher or lower depending upon relative degree, so we cannot say that least strength species is most likely to survive.
(E) If a species does not survive an ecological disaster, it is because that species' resource requirement for maintaining its strength outweighed the resources available - It is to specific. Moreover, it is one of often cases.
_________________
Hard-work, Perseverance and Commitment.....