How can the project manager help to keep momentum in the project and help to keep the customer involved?

How can the project manager help to keep momentum in the project and help to keep the customer involved?
A . Leverage agile cycles to build and test the solution
B . Increase the number of Q-Gates
C . Add customer resources to the project to reduce the need for formal training
D . Walk through the solution processes with the stakeholders

Answer: A,C