Which of the following is physical capital?
a. a college degree
b. a factory building
c. learning to sew
d. playing the violin

A physical capital has to be something that is "physical", that is - it has to be possible to touch and for example move somewhere else.

The example of a physical capital here (and the correct answer) is a factory building (it might be hard to move, but it can at least in theory be moved).

The answer is to spread the world of christ