A
A.$cal {A}(a_{1},a_{2},a_{3})=(2a_{1}-a_{2}+a_{3},a_{2}-a_{3},2a_{1}+a_{3})$
B
B.${cal A}(a_{1},a_{2},a_{3})=(a_{1},0,a_{2})$;
C
C.${cal A}(a_{1},a_{2},a_{3})=(a_{1},2a_{2},3a_{3})$
D
D. ${cal A}(a_{1},a_{2},a_{3})=(a_{1}^{2},a_{2}-a_{3},a_{3}^{2})$
