What is the difference between parent material

Parent material is the geologic material from which soil horizons form. Many soils have more than one parent material, for example loess over till. ... Every soil horizon has a parent material, but the same parent material usually appears different in different horizons because soil formation processes have altered it.

Explanation:

the answer is b because, investigating whether another species of moth also drinks tears might be interesting, but it would not directly explain why this species of moth does.

to explain why this species of moth drinks tears, the scientist could ask: "what nutrients that moths need are in elephant tears? "

the scientist could experiment with moth repellent or oter ways to keep the moths away, but that would not answer his original question.