Final answer:
The competitive environment is the factor influencing the number and types of competitors a marketing manager encounters, encompassing actions of rivals, market conditions, and resource availability (b).
Step-by-step explanation:
The environment that affects the number and types of competitors a marketing manager must face and how they might behave is called the competitive environment.
This environment is dynamic, including various factors such as the actions of rival businesses, supply and demand conditions, entry or exit of firms, and changes in market share. In the context of ecosystems and social studies, the concept of competition also pertains to the struggle for existence and the natural selection process where organisms compete for limited resources such as food, water, sunlight, and space.