Final answer:
A linear relationship between Vmax and enzyme concentration is expected when the substrate concentration [S] is much greater than the Michaelis constant (Km), which is when [S] >> Km.
Step-by-step explanation:
A linear relationship between Vmax (maximum velocity) and enzyme concentration would be expected when the substrate concentration [S] is much greater than the Michaelis constant (Km), which is when [S] >> Km. This condition ensures that all enzyme active sites are saturated with substrate, resulting in a situation where the reaction rate is directly proportional to the enzyme concentration. Hence, the Vmax will increase linearly with an increase in enzyme concentration because it's dependent on the availability of enzyme molecules.
Km is a measure of the affinity of the enzyme for its substrate; a smaller Km value indicates higher affinity. When [S] >> Km, the enzyme's active sites are fully occupied, and the equation simplifies to show that Vmax is directly proportional to the enzyme concentration. In the context of the given options, the correct answer is option 2) [S] >> Km.