What Is the Principle of a Continuous Monitoring Blood Culture

What is the principle of a continuous monitoring blood culture system?

A) The amount of CO₂ produced is measured as a growth index and compared with a threshold.
B) The amount of increased lipopolysaccharide is measured and compared against the null value.
C) The pH of the media is continuously measured to check for bacterial metabolic by-products.
D) An optical monitor records the number of bacteria and records the growth.