The pH of acid J is 4. The pH of acid K is 6. How much more acidic is acid J than
acid K?

100 Times more Acidic

Explanation:

The pH scale is logarithmic in every 10.  So, from 4 to 5 is 10 times less acidic.  From 5 to 6 is another 10 times less acidic.  So in total, it is 100 times less acidic.

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.