A storm brings two formerly separated populations of beetles together. They look very similar. Under the biological species concept, which of the following would show that the two populations are different species? A. One population breeds in spring, the other in fall.
B. Males of the two populations have different flight patterns in courtship.
C. When individuals from the two populations mate with each other in the laboratory, the eggs fail to hatch.
D. All of the above is correct.
E. None of the above is correct.

The correct option is D: All of the above is correct.

Explanation:

The biological species concept says that species are population groups that, in a real or potential way, can reproduce among each other and that are reproductively isolated from other groups.

Individuals belonging to a species cannot mate with members of other species, and if they do there is not any reproductive success.    

The mechanisms of reproductive isolation might be divided in prezygotic and postzygotic.

Prezygotic or Premating mechanisms:

Ecological or due to habitat isolationSeasonal or temporal. This is the case described in option A "One population breeds in spring, the other in fall". These species are reproductively isolated because they differ in their breeding season.Sexual or ethological. This is the case described in option B "Males of the two populations have different flight patterns in courtship". Males belonging to each species behave differently during courtship. MechanicalGametes incompatibility

Zygotic or Postmating Mechanisms:

Hybrid inviability. This is the case described in option C which states that "When individuals from the two populations mate with each other in the laboratory, the eggs fail to hatch". Eggs fail to hatch because the zygote is inviable. Hybrid sterilityHybrid decreased fertility