Project managers need exceptionally good communication and negotiation skills primarily because?

because,

He must engage in constant communication with the members via group meetings, conferences etc

He is supposed to lead a team of professionals and make crucial decisions. so he must have great man-management skills and strong communication skills verbal or otherwise.

He is supposed to interact or negotiate with the sponsor or customers, and needs to be on the winning end of a healthy negotiation

He represent the whole team in terms of intentions, opinions and must make sure consensus among the members for healthy progression of the project

d.  Procurement activities mandate this

Thank you for the invitation

Option C

Project Manager are Middle level Managers and they delegate scope of work hence good communication and negotiation is a must for smooth transitions into the activity and follow up for results and outcome in the project targets.

Appreciation for the invitation. Option C - more relevant answer for the Project Manager Skills Required.

Thanks For the Invite.

B is the ideal option

In my opinion 

They may be leading a team over which they have no direct control

I think B and C.

B. They must provide executive/customer/sponsor briefings

Of course you need good communication and negotiation skills for Stakeholder Management.

C. They may be leading a team over which they have no direct control

I think sometimes here you also need good negotiation skils. Especially if you are working in a Functional Organization which is not very common with working in projects. In this case you often have not direct control of your team members and you have to negotiate with the Functional Managers about every human resource you need for your project. And of course you need excellent communication skills to lead a team under these circumstances.

Thank you for invitation. I think option B. They must provide executive/customer/sponsor briefings is good answer.

Thank you for the invitation. B is the suitable answer.

B. They must provide executive/customer/sponsor briefings