To scale up the AWS resources using manual AutoScaling, which of the below mentioned parameters should the user
change?

A.
Maximum capacity

B.
Desired capacity

C.
Preferred capacity

D.
Current capacity

Explanation:
The Manual Scaling as part of Auto Scaling allows the user to change the capacity of Auto Scaling group. The user can
add / remove EC2 instances on the fly. To execute manual scaling, the user should modify the desired capacity.
AutoScaling will adjust instances as per the requirements. If the user is trying to CLI, he can use command:
as-set-desired-capacity <Auto Scaling Group Name> –desired-capacity <New Capacity>
http://docs.aws.amazon.com/AutoScaling/latest/DeveloperGuide/as-manual-scaling.html