Choose the best answer. Explain why it is the best answer. We care about the reasoning more than just having the right answer.

4. Which of the following are correct?

A. The exchange of ideas within firms is more important than the sharing of knowledge between people in different firms, so must also be more important for urban agglomeration.

B. Large cities can be expected to have a smaller number of occupational job titles because the opportunities for exploiting increasing returns to scale are greater there.

C. Rents are higher in large cities, so firms need to economize on space, and do so by limiting the number of different goods available. As a result, consumers and firms should find selection to be more limited in large cities.

D. None of the above.