The carrying capacity is controlled by limiting factors, factors that can constrain a population's size or slows/stops it from growing. The limiting factors can be biotic (like competition for resources, food availability, predation, etc) or abiotic (like altitude, space, temperature, natural disasters, etc). All of those factors can interefere in the size of a population. Therefore, the correct answer includes all of the options:
1. Climate
2.Available food supply
3.The number of predators
4. Available shelter
They're all correct.