The correct option is A senescence
Senescence is the natural biological process of aging in which cells lose the power of cell division which eventually leads to death. For example, older leaves or other plant parts undergo senescence.
Inflorescence is an arrangement of flowers on the floral axis (the area bearing flowers).
Dormancy is the state of an organism in which physiological activity is suspended for a time period.
Plasticity is the ability of plants to form different kinds of structures in response to environmental factors (like climate, water availability, etc.) or phases of life.