Power Electronics - Engineering

Q1:

A 3 phase dual converter consists of

A two 3 phase semiconverters connected in parallel

B two 3 phase semiconverters connected in antiparallel

C two 3 phase full converters connected in antiparallel

D two 3 phase full converters connected in parallel

ANS:C - two 3 phase full converters connected in antiparallel

How come? Please explain it.