Final answer:
The carrying capacity (K) truly can vary as it represents the maximum population size that can be sustained by the available resources, which can fluctuate.
Step-by-step explanation:
The statement that the carrying capacity (K) of a population can vary depending on the supply of resources is true. Carrying capacity is defined as the largest population size that can be supported in an area without harming the environment or the maximum number of individuals of a species that an environment can support with its limited resources. It is not fixed and can change due to various factors such as availability of water, food, space, and other essential resources. When a population is small, it can grow exponentially as its size is much less than the carrying capacity; however, as it reaches or exceeds K, the population growth can slow down significantly or even decline.