Answer is: a) in the presence of a base.
Phenolphthalein is colorless in acidic solutions and pink in basic solutions.
Acid-base indicators are usually weak acids or bases and they are chemical detectors for hydrogen or hydronium cations.
Example for acid-base indicator is phenolphthalein (molecular formula C₂₀H₁₄O₄).
When solution turns phenolphthalein pink, it means it is basic (pH>7).
I believe it would be the first option. It forms iron oxide (rust) when exposed to moisture and air.
We will see that the volume of the unit cell is 144,070,699.06 pm^3
<h3>
How to get the volume of a body-centered cubic unit cell?</h3>
In a body-centered cubic unit cell, the side length of the cube is given as:

Where R is the radius of the atom.
And the volume of a cube is the side length cubed, then we can see that the volume of our cube will be:

Solving that we get:

This is the approximated volume of the unit cell.
If you want to learn more about unit cell structures, you can read:
brainly.com/question/13110055
The answer is likely to be A