Which power supply slots in the enclosure must be populated to meet the requirement for N+1 redundan

A customer wants a basic power configuration for a c7000 enclosure using only single-phase
power. Which power supply slots in the enclosure must be populated to meet the requirement for
N+1 redundancy?

A.
1 and 3

B.
1 and 2

C.
1 and 6

D.
1 and 4