Which upgrade is possible for a customer with IBM FlashSystem 840?
A. Systems purchased with eight 2 TB flash modules can be expanded to twelve 4 TB flash modules.
B. Systems purchased with eight 4 TB flash modules can be expanded to twelve 2 TB flash modules.
C. Systems purchased with eight 4 TB flash modules can be expanded to twelve 1 TB flash modules.
D. Systems purchased with eight 2 TB flash modules can be expanded to twelve 2 TB flash modules.