The correct option is D Ketoglutaric acid Succinic acid
When a single round of Krebs' cycle completes, only 1 ATP/GTP is produced by substrate level phosphorylation. Ketoglutarate dehydrogenase (6C) is converted to succinyl CoA which is then converted to succinic acid (4C) by phosphorylating 1 ADP to ATP. So the answer is 'Ketoglutaric acid Succinic acid'.