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Option A is incorrect. The passage suggests that disruptive innovation is indeed useful to the customers, and brings in a new wave of innovation.
Option C is incorrect. Since the passage says that DI is more easily carried out by start ups, this option conveys a point that is directly opposite to the passage.
Option D is incorrect. The passage explicitly states that smaller companies are better off entering new markets.
Option B is the only option that is mentioned in the passage. It states that DI has lower profit margins, and initially has smaller markets. Hence, it is the correct answer.