Correct option is A
Creep, the slow and progressive deformation of a material under constant stress at high temperatures, occurs in three stages:
1. Primary Creep: This is the initial stage where the creep rate is high but decreases with time as the material undergoes strain hardening.
2. Secondary Creep: Also known as the steady-state creep, this stage is characterized by a constant creep rate. It is the longest phase and is crucial in determining the material's lifespan under stress.
3. Tertiary Creep: In this final stage, the creep rate accelerates rapidly leading to eventual failure or rupture of the material due to the formation of internal voids or cracks.
