Bacteria that are helpful in one place may be harmful in another. What information in the text supports this statement?
A Heliobacter pylori is a bacterium that causes gastritis (irritation or
inflammation of the stomach lining) and peptic ulcers, diseases which were once
thought to be caused by too much acid.
B Streptococcus salivarius appears to help prevent tooth decay in the mouth
but can be dangerous to people with weakened immune systems if it gets
outside the mouth.
Bacillus subtilis releases toxic chemicals to kill fungus, possibly including
Trichophyton interdigitale and other species that cause athlete's foot.
D Skin, which is our interface with the world, supports a large number of the
human body's most diverse populations of bacteria, including Bacillus subtilis.