Determine which of the following transformations are linear transformations.?

Determine which of the following transformations are linear transformations.

A. The transformation T defined by T(x_1, x_2, x_3 ) =(1, x_2, x_3)
B. The transformation T defined by T(x_1, x_2 ) = (4x_1- 2x_2, 3 |x_2|).
C. The transformation T defined by T(x_1, x_2 ) = (2x_1-3x_2, x_1+4, 5x_2).
D. The transformation T defined by T(x_1, x_2, x_3 ) =(x_1, 0 , x_3)
E. The transformation T defined by T(x_1, x_2, x_3 ) =(x_1, x_2, -x_3)