The correct answer is : Mitosis, cell growth and differentiation.
Plants increase in height due to the activity of meristem or meristematic tissue. Meristems are tissues which have capacity to divide throughout their life. Meristems are located in the apical meristems, shoot apex and root apex. Meristems divide through mitosis. The daughter cells enlarge, stretch and differentiate into other types of cells as they mature. This causes some plants to increase in height.
