The answer is noble gas. Since noble gas are constant and
unreactive. They can still shape compounds with other elements.
Group 15 is also group 5A and Group 17 is also group 7A. Elements in these sets
do not typically form ionic bonds; they are more on creating covalent bonds
since they're non-metals.
Therefore, that leaves us with B. from Group 1. They are metals (but Hydrogen)
which respond violently with water, and they form ionic bonds, for they drop
outer electrons easily.
The constant is the temperature of the air that the plants get.
The independent variable is the thing that YOU control. That's the amount of sunlight each plant gets.
The <em>dependent variable</em> is anything that's caused by changes in the independent variable. That's the growth of the plants.
