True statement about first order kinetics is:: (A) A constant amount of a drug is eliminated in unit time, (B) The half-life increases with an increase in dose, (C) The rate of elimination is constant, (D) The rate of elimination is proportional to the plasma concentration
Answer is D. Drugs may follow zero order or first order kinetics. It depends on the following formula:
Rate of Elimination α {Plasma Concentration}order

Thus, if a drug follows zero order kinetics, {Plasma Concentration}0 is equal to one, in other words rate of elimination is independent of plasma concentration or rate of elimination is constant.
From the above formula, rate of elimination is proportional to plasma concentration for the drugs following first order kinetics.