Widened margins does not occur at the continental margin
I think the independent variable is the temperature, while the dependent variable is the size of the balloon. The factor that is held constant is the amount of air in the balloon. An identical balloon kept at the original temperature. Independent variable in an experiment is the variable that the experiment plans to change while the dependent variable is the variable whose value depends on the independent variable.
C.
Biotic mean alive, so we can cut off the first 2 easily. Aquatic birds eat frogs, so that one is safe for now. A decrease in something parasitic usually helps the population, so D is out too. The only one left is C.
This is true. There are a few websites online that talk about how it happens, I suggest looking them up.
