Solution

Plants have three types of meristems, the apical meristem, the lateral meristems and the intercalary meristem. Leaves are derived from shoot apical meristem which swells to form undifferentiated leaf primordium which divides into two systems that develop leaf blades and leaf sheaths. The growth of leaf blades occurs due to cells division but is mainly from cell elongation. Thus, the growth of leaf is first restricted to an apex of primordium and but is short-lived and is followed by intercalary growth which in turn causes a growth of leaf length.
Thus, the correct answer is option A.