Which of the following is NOT cited as an example of invalid sales promotions
A. There is yet no scientific consensus on the questions about "probiotic" products.
B. Antibiotics are not very selective as to which bacteria they attack.
C. It is impossible to know how many live bacteria will be preserved in the digestive system.
D. It is not always easy to measure to what extent probiotic products can outrun potentially unfriendly microbes.