Answer: Possession of Valves
Explanation: Veins possess valves which ensures that blood flows in only one direction. Valves helps blood to flow back to the heart against gravitational force.
Arteries don't have valves because the pressure originating from the heart is capable of causing the blood to flow in one direction.
Answer:
a. He is missing a control group of mice that did not receive the new antibiotic.
Explanation:
In any experiment especially experiments testing effectiveness of a drug, there should be a control group.
The importance of a control group is to minimize the effects of other variables other than the independent variable hence increasing reliability of the results.
in this case, a group of mice that did not receive the new antibiotic would have served as the control group.
I’d talk about how enzymes have that induced fit model. A substrate is unique to that specific enzyme. The substrate binds to the enzymes active site (or sometimes allosteric site) which in turn alters the conformation or shape of that particular enzyme