According to one hypothesis, the growth rate dV/dt of a cell’s volume V is proportional to its surface area a. Since V has cubic units such as cm³ and A has square units such as cm², we may assume roughly that A ∝ V^2/3, and hence dV/dt = kV^2/3 for some constant k. If this hypothesis is correct, which dependence of volume on time would we expect to see (again, roughly speaking) in the laboratory?

(a) Linear 

(b) Quadratic 

(c) Cubic