Which of the following methods are used for protection against fracture?
1. Avoid sharp corners and notches in the part to eliminated points of stress concentration.
2. Provide better finish to the surface by polishing
3. Introduce residual tensile stresses on the surface.
(a) 1,2 and 3 (b) 1 and 3 only
(c) 2 and 3 only (d) 1 and 2 only