The benefit of measuring the initial rate of a reaction V₀ is that, at the beginning of a reaction:

A) [ES] can be measured accurately.
B) changes in [S] are negligible, so [S] can be treated as a constant.
C) changes in K_m are negligible, so K_m can be treated as a constant.
D) V₀ = V_max.
E) varying [S] has no effect on V₀.