Final answer:
High entry barriers and limited market size can affect rivalry in an embryonic stage by restricting competition and possibly leading to monopoly or oligopoly situations.
Step-by-step explanation:
The question 'What affects rivalry in an embryonic stage?' is related to the dynamics of market competition in business environments. Barriers to entry are significant factors in this context, as they can either discourage new entrants and maintain high profits for existing firms, leading to monopoly-like situations, or they can be low enough to allow a competitive market to flourish. Considering the options provided in the question, high entry barriers and limited market size can greatly affect rivalry at the embryonic stage of a market by restricting competition and possibly leading to a monopoly or an oligopoly. On the other hand, low entry barriers and high market growth typically encourage competition and market entry, reducing the likelihood of any single firm dominating the market.