See explanation below.
Work Step by Step
(a) The concentration of C goes from a finite value, say [C]o to 0 in a given time, say to. The average rate of the reaction is the overall change in concentration of C, divided by total time taken. This is equal to [C]o/to (b) The reaction rate at point x is an instantaneous rate, the rate is equal to the slope of the tangent drawn on the curve at point x. Reaction rate=-dC/dt at t=x (c) The initial rate is an instantaneous rate, given by the slope of tangent at point t=0. Reaction rate= -dC/dt at t=0 (d) One mole of C gives one mole of D. SO the rates will have same value, be it consumption of C or formation of D.