Many bacteria do not interact with humans, but those that do can always be classified as either harmful or not harmful to humans. true or false?
select one:
a. true. they always either hurt us or they don't.
b. false. some are fine in small numbers, but in big numbers they can overwhelm the immune system and cause problems.
c. false. some get worse as they age.
d. true. once they mutate to be harmful, they stay that way.

The answer is letter B.

Some bacteria that interact with humans can cause benefits to the body when they are small in numbers. An example of this bacteria is the lactobacilli which can be found as an ingredient in some drinks that can purify the digestive system. Though, they can only be taken in small amounts because they may overwhelm the immune system which can cause major complications within the internal organs. Some bacteria that interact with humans can be harmful because of their capacity to divide at a fast rate.

The answer would be sand and gravel