Your nose and your mouth are both a portal of entry into your body. If you cover one and not the other it defeats the purpose because Bacteria can still enter the system. They are both part of your respiratory system.
Answer:
temperature
pH
concentration
Explanation:
Enzymes work best within specific temperature and pH ranges, and sub-optimal conditions can cause an enzyme to lose its ability to bind to a substrate.
Adaptors are unconscious, and can be signs of many things as they are menial gestures we create in response to certain situations. It's a form of nonverbal communication that doesn't really fall into any one category besides the first. My best guess is A, by this understanding.
