The correct option is C Blackman
Every factor affecting photosynthesis has three cardinal points namely minimum, optimum, maximum. The process starts when minimum conditions are available, proceeds at its best at optimum and almost stops at maximum. Blackman's law of limiting factor is based on Liebig's law of minimum. According to Blackman, 1905, when a process is conditioned as to its rapidity by a number of factors its rate is governed by the minimum available factor. Blackman's law of limiting factors determines the rate of photosynthesis.