A. Earth worms
Because it can only flow one way
The most common way to get your blood flowing is by exercising, improving your diet, have a hot bath, etc.
<span>One group is given a larger dosage than is typically prescribed.
A second group is given a smaller dosage than is typically prescribed
Then results of the groups are compared to each other.
The thing that is missing in this experimental design is a third group who are tested with the typical dosage.</span>
Two of the above are true
