Tập nào sau đây là không gian con của 3\: a. ( ){ }3123 1,, / 1W==⊂\ b. ( ){ }3123 1,, / 0W==⊂\ c. (){}3123 1 2,, / 1W=+=⊂\ d. ( ){ }3123 2,, / 3W==

Thermal stresses are developed in a metal when its a) initial temperature is changed b) final temperature is changed c) density is changed d) thermal deformation is prevented e) expansion is prevented f) contraction is prevented