It should be 3! That is the only logical answer to the question...
I believe that you're question is referring to homeostasis
The independent variable in the hypothesis of an observed increased in sea turtle sickness once an increase in red tide can be seen would be the increase of red tide.
The reason for this is that red tide increases or decreases will happen independently of the amount of sea turtle sickness - therefore increasing sea turtle sickness will be dependent on the first variable. (independent one).
A prothallium, or prothallus<span> is usually the </span>gametophyte<span> stage in the life of a </span>fern<span> or other pteridophyte. Occasionally the term is also used to describe the young </span>gametophyte<span> of a liverwort or peat moss as well.</span>
