Final answer:
Two key reasons why marketers must stay vigilant of the competitive environment are the rapid technological advancements and the global expansion of markets, both of which have drastically increased competition. Additionally, regulatory changes also play a role and should be monitored.
Step-by-step explanation:
Marketers must pay attention to the dynamic competitive environment for several crucial reasons, of which two are discussed here. The first is technological advancements, which have significantly changed the landscape of most marketplaces. The rise of the internet and improved communications technologies have allowed consumers to purchase goods and services from across the globe, increasing the level of competition faced by retail businesses. The second is globalization, which allows businesses to operate on an international scale, further intensifying the competitive environment as companies are no longer just competing locally but potentially with suppliers and buyers from around the world.
Another reason, not directly mentioned but implied by these factors, is regulatory changes, which can arise as a response to such global technological shifts. This can affect market access, competition, and operational costs. Therefore, the correct answer from the options listed would be 'd. All of the above'.