Determine if the linear system

is in echelon form.

First choose which of the following statements are correct. If there is more than one reason why the system is not in echelon form, type the letters as a comma separated list. If the system is in echelon form, make sure to type D as your answer.

A. The system is not in echelon form because a variable is the leading variable of two or more equations.
B. The system is not in echelon form because the system is not organized in a descending "stair step" pattern so that the index of the leading variables increases from the top to bottom.
C. The system is not in echelon form because not every equation has a leading variable.
D. The system is in echelon form.

Correct Letter(s):

If the system is in echelon form, also identify the leading variables and the free variables in the corresponding answer blanks below. Type x1, x2, and x3 to enter the variables $x_1$, $x_2$, and $x_3$ and separate multiple variables by using a comma. If the system is in echelon form and no such variable exist, type none. If the system is not in echelon form, type NA in both answer blanks.