Which approach should you recommend?

You are designing an Azure web application. The application uses one worker role. It does not use SQL Database. You have the following requirements:
Maximize throughput and system resource availability
Minimize downtime during scaling
You need to recommend an approach for scaling the application.
Which approach should you recommend?
A. Increase the role instance size.
B. Set up horizontal partitioning.
C. Increase the number of role instances.
D. Set up vertical partitioning.