Question 16.

A noticeable clue to ensure that the male northern elephant seal dialects did not disappear is presented in the penultimate paragraph: ["...At the individual level, the pulse of the calls stayed the same: A male would maintain his vocal signature throughout his lifetime. But the average pulse rate was changing. Immigration could have been responsible for this increase, as in the early 1970s, 43 per cent of the males on Año Nuevo had come from southern rookeries that had a faster pulse rate... "]. The loss in the dialect is due to the influx of seals with a faster pulse rate and "as the population continued to expand and the islands kept on receiving immigrants from the original population, the calls in all locations would have eventually regressed to the average pulse rate of the founder colony." Thus, if the individual pulse rate of the immigrants varies or adapts to the existing population, this could preserve the dialect in a particular region. The statement in Option D reflects this specific idea and helps sustain the existing dialect in a given population. Options A and C do little to contribute to the cause of preventing the disappearance of the dialects.  Option B aligns with the discussion in the passage and is responsible for the regression of the dialects. Hence, Option D is the correct answer.