If We Know That $\mathbf { a } \times \mathbf { b } = \mathbf { a } \times \mathbf { c }$

Multiple Choice

If we know that $\mathbf { a } \times \mathbf { b } = \mathbf { a } \times \mathbf { c }$ , which of the following statements is true?

A) b and c are parallel
B) $| \mathbf { b } | = | \mathbf { c } |$
C) b = c
D) a is parallel to b - c

E) a is a unit vector