Examples are used to "exemplify" a situation. Hence, we take an abstract theory and we make it more approachable by showcasing some details. Hence, we have that the example makes abstract idea more concrete. The first 2 choices are wrong since they state the opposite. The 3rd choice is rather irrelevant, examples can make it more or less didactic. Hence, the 4th choice is correct.
When you say physical capital, it refers to the additional machinery, building, space etc.
Therefore an example of changing physical capital is B. Building extra space in the factory. By doing this, you are adding additional physical location in where your employee or worker can work.
