During the execution of a project, a risk is identified by a team member. This newly identified risk is currently not in the Risk Register.

I would go for option B and analyze the risk. 

Because according to the ISO31000 risk management guidelines the risk analysis process includes both A and C options and will pave the way for completion of option D 

I would first analyze the risk. And then get into meeting with the team to discuss on the impact and probability. Once the risk is found relevant, the Risk Register will be updated.

1. Analyze the Risk.

2. Discuss with Team and if it required with Stake holders to ascertain the impact/probabilities. 

3. Prepare the mitigation of this Risk.

4. Update the Risk Register. If this Risk is impacting any schedules and agreed by timelines up date the project plan.

Ans. Option B is the right choice (Analyse the risk)

a) Discuss the risk with the team to ascertain the impact and probability of the risk

However Creation of a Contingency Plan to deal with the risk should it occur.Taking early steps to reduce the probability of an adverse risk occurring may be more effective and less costly than repairing the damage after a risk has occurred.

However, some risk mitigation options may simply be too costly in time or money to consider.

I THINK DISCUSS IT WITH THE TEAM AND TAKE STEPS TO REDUCE SUCH TYPE OF RISKS

 D.

Update the Risk Register in the system

As a manager i must stop the work in progress instantly and registered the risk.After that i should go for a meeting with each and every member of the project that they should aware about what constitutes a risk to the project or factor that could potentially impact the project in a positive or negetive way.

D- Update the risk register is the first thing to be done as per PMBOK

Analyze the risk first... will my first priority.