Which statements accurately explain why regulatory breakup of digital firms is likely to be ineffective?

a. Companies in digital industries become obsolete and disappear rapidly before they can develop monopoly power.
b. Digital industries have a tendency to be highly concentrated.
c. The individual firms would change, but the industry would retain the same level of concentration.
d. Positive network effects would reconcentrate the industries over time.
Digital industries have a tendency to become less concentrated over time.