Explanation/Reference:
Explanation:
Due to the reason that risk is constantly changing, it is being evaluated annually or when there is significant change. This gives best alternative as it takes into consideration a reasonable time frame of one year, and meanwhile it also addresses significant changes (if any).
Incorrect Answers:
A: Evaluating risk only when there is significant changes do not take into consideration the effect of time.
As the risk is changing constantly, small changes do occur with time that would affect the overall risk.
Hence risk evaluation should be done annually too.
B: Evaluating risk once a year is not sufficient in the case when some significant change takes place. This significant change should be taken into account as it affects the overall risk.
D: Risk evaluation need not to be done every four to six months for critical processes, as it does not addresses important changes in timely manner.

Explanation/Reference:
Explanation:
Risk register is not an input to risk identification, but it is an output of risk identification.
Incorrect Answers:
A, B, C: These are an input to risk identification.
Identify Risks is the process of determining which risks may affect the project. It also documents risks' characteristics. The Identify Risks process is part of the Project Risk Management knowledge area. As new risks may evolve or become known as the project progresses through its life cycle, Identify Risks is an iterative process. The process should involve the project team so that they can develop and maintain a sense of ownership and responsibility for the risks and associated risk response actions. Risk Register is the only output of this process.