Answer:
The independent quantity in the situation is the length of the diameter.
Step-by-step explanation:
Consider a relationship between two variables.
Of the two variables one variable is dependent upon the other.
Dependent variables are those variables that are under study, i.e. they are being observed for any changes when the other variable values are changed.
Independent variables are the variables that are being altered to see a proportionate change in the dependent variable.
In this case, it is provided that Grissom knows there is a relationship between the volume of the sphere and the length of its diameter.
With every sphere that Grissom draws, the volume of the sphere changes according to its diameter length.
That is the volume of the sphere depends upon the length of its diameter.
Thus, the independent quantity in the situation is the length of the diameter.