What type of engine specifications were eligible for the 1975 SCCA/USAC Formula 5000 Championship?

A. Either 5 liter (305 cid) American stock block engines or USAC's 161 cid turbocharged, 255 cid DOHC, or 320 cid stock block engines
B. Only 5 liter (305 cid) American stock block engines
C. Only 255 cid DOHC engines
D. Only 161 cid turbocharged engines
Answer: 