What is the standard cell potential of a cell made of theoretical metals ma/ma2+ and mb/mb2+ if the reduction potentials are –0.19 v and –0.85 v, respectively?

The standard cell potential of a cell made of theoretical metals ma/ma2+ and mb/mb2+ is to be determined. We are given their reduction potentials:

-0.19 v for A
-0.85 v for B

To solve for the standard cell potential, examine the reaction and

the standard cell potential for this case is (-0.19- (-0.85)) v = -0.66 v

The answer is b because c don't explain why the moths are on them and it isn't a because as we know only one species of moth does this

Not a  mixture of two common elements that can be separated by physical means.