Which of the following is displaced by 'Cu'? 1.Fe2+ 2.Ag+ 3.Zn2+ 4.Al3+

Explanation:

This problem tests our knowledge/understanding of the electro-chemical series.

Electrochemical series or activity series is a list that describes the arrangement of elements in order of their increasing electrode potential values.

In the electro-chemical series metals placed above can displace metals below from their salt solutions.

In this question given the series as  stated

1. Fe2+

2.Ag+

3.Zn2+

4.Al3+  

In the series we have metals stated as Zn>Fe>Cu>Ag.

Cu will displace silver Ag+  because it is below it in the series

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.