1.) Air can be separated into its constituents such as oxygen, nitrogen etc.
2.) Air has a variable composition because at different places different amount of gases are present in air.
I believe the correct response would be A. The ions once dissolved in the solution are free to move
Answer:

Explanation:
Given that,
A typical coffee mug holds about 355,000 microliters of liquid.

Also, 1 L = 0.001 kL

So, a typical coffee mug holds about
or
of liquid.
We need to convert it into Scientific notation.
We will shift 4 zeros to right. As a result,

So, the mug will hold
of liquid.
Edit : OPTION C is the answer
Option B is the best, Even though the cost is 30 Billion it essentially takes Lesser time to construct. For Plan A, They would have to construct the overground railway and then take a lot of time and effort to create wildlife corridors and then plant trees. Plan B takes much less time compared to plan A and might as well have a lesser impact on the environment!