Juvenile monkeys that are separated from their mothers will often show

I guess between A and B,
A only talks about one reason why juvenile monkeys show less self-destructive behavior
But B is more relevant to the conclusion because it explains the "still observable" part of the conclusion, which generalizes the WHOLE arguments and says that: The presence of mixed gender group unrelated adult female monkeys is more important to juvenile monkeys in alleviating distress caused by being separated from their mothers than is the presence of unrelated juvenile monkeys. (less stress therefore least prevalent)
The trick is not to stop at one justification, but look at the conclusion as a whole

OFFICIAL EXPLANATION

The question stem presents a series of premises about how juvenile monkeys behave when separated from their mothers; specifically, the behaviors are more or less prevalent under various conditions. We are asked for the hypothesis that would best explain the variations in behavior. Although we are not asked to draw a conclusion from the premises, we should look for an explanatory hypothesis using the same constraints: assume as little as possible and take no unnecessary logical leaps.

(A) This choice confuses alleviation of self-destructive behavior with causation of that behavior. The question stem attributes the behavior to separation from the mother, not to the presence of other monkeys.

(B) Correct. We are told that separation from the mother causes self-destructive behavior that is lessened some in the presence of other, unrelated juveniles and adult males, and lessened even more in the presence of a mixed group of unrelated, adult monkeys. Since adult male monkeys are present in both cases, they may be disregarded as a cause of the difference in degree of self-destructive behavior. The best hypothesis is that the distressed juveniles are more comforted by the adult females than by the other juveniles.

(C) We have no reason to believe that any other monkeys are “threatening”—merely that some monkeys alleviate distress better than others.

(D) This choice is on the right track, but its language is too strong. We know that the presence of unrelated adult female monkeys is more soothing than the presence of other monkeys to a juvenile that has been separated from its mother, but we don’t know if the juveniles are comforted to such a degree that the unrelated females are a “suitable substitute.” (For instance, perhaps the presence of other juveniles alleviates the behavior by 5%, and the presence of the unrelated females by 10%).

(E) The situation described does not mention reuniting monkeys with their mothers. Stay away from choices that require making additional, unnecessary assumptions.

I think this question is problematic.

To explain the hypothesis the explanation should be both inferable from the passage and must be true in certain condition.
But, in the passage, we can only infer that either mixed gender or age of monkey (at least) can affect monkey`s behavior.
We can not conclude which one(or both)really affect the behavior.

B seems not crystal clear answer for me

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