Millions of female bats rear their pups in Bracken Cave. Although the

It is a method question. We need to see how the argument is structured.

Millions of female bats rear their pups in Bracken Cave.
Every morning, each mother is almost always swiftly reunited with her own pup.
The bats’ calls are their only means of finding one another.
A bat pup cannot distinguish the call of its mother from that of any other adult bat.

Conclusion: So each mother bat can recognise the call of her pup.

(A) derive a general conclusion about all members of a group from facts known about representative members of that group

The argument talks about the female bats and their pups in Bracken Cave and their behaviour. It does not talk about representative few and derive a general conclusion about all members. The discussion is only about female bats in Bracken Cave.

(B) establish the validity of one explanation for a phenomenon by excluding alternative explanations

Correct. The argument excludes alternative explanations - there are no other means on finding one another other than calls, a bat pup cannot distinguish the call of its mother etc.
It then arrives at the only leftover explanation for the phenomenon of mother reuniting with pups - mothers recognise the pup calls

(C) support, by describing a suitable mechanism, the hypothesis that a certain phenomenon can occur

The phenomenon of mothers reuniting with bats actually does occur. Hence the argument does not try to support that it can occur. It gives explanation for how the phenomenon does occur.

(D) conclude that members of two groups are likely to share a certain ability because of other characteristics they share

No. The argument doesn't talk about any other characteristics.

(E) demonstrate that a general rule applies in a particular case

No general rule discussed.

Answer (B)

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