The correct option is
C Intussusception
A. Accretion is the process by which gradual growth or enlargement takes place by the accumulation or adhesion of external parts (secondary cell wall in plants).
B. Introgression or introgressive hybridization can be defined as the movement of a gene from one species into a gene pool of another species by repeated backcrossing.
C. Intussusception can be defined as the process by which the cell wall grows due to the deposition of cellulose (primary cell wall in plants).
- So, the correct answer is 'Intussusception'.