Final Answer:
A system is in a safe state only if there exists a safe sequence. Option C is answer.
Step-by-step explanation:
In the context of operating system resource allocation, a system is considered in a safe state if there exists a safe sequence of processes. A safe sequence is a series of process executions that can be carried out without violating the resource allocation constraints and causing a deadlock.
Option a) refers to "safe allocation," which is not a standard term in this context.
Option b) mentions "safe resource," which is not a criteria for defining a safe state.
Option c) correctly identifies the concept of a safe sequence as a prerequisite for ensuring a system is in a safe state, making it the correct answer.