Final answer:
An emergent property is a property that a system has but that its individual component parts do not have. It emerges as a result of the interactions and organization of the system's components.
Step-by-step explanation:
An emergent property refers to a property that a system has, but its individual component parts do not have. It is a property that emerges as a result of the interactions and organization of the system's components.
For example, consider a human brain. The individual neurons in the brain do not have the ability to think or process complex information on their own. However, when billions of neurons come together and interact in a specific way, the emergent property of consciousness arises.
Therefore, option a. 'A property that a system has but that its individual component parts do not have' accurately defines an emergent property.