The correct option is B Human blood
Human saliva has a pH of 6.7, it is lower because bacteria in the mouth produce some acids.
Urine has an average pH of 6.0.
Gastric juice is highly acidic with a pH of 1.5-2.5 due to the HCl present.
Human blood has a pH range of 7.35 to 7.45. Therefore blood has the highest pH amongst these.