Given the structure of the automobile industry, entering the auto manufacturing industry seems risky. Yet, Tesla Motors joined the fray. Rather than attempting to compete head-on with internal combustion engines, Tesla Motors entered the all-electric car segment, a much less-crowded niche in the overall car industry. Which of the following forces is most relevant to Tesla's decision to enter this all-electric segment?

Rivalry among existing competitors

Threat of entry

Power of buyers

Threat of substitutes