matrix rank

$$A = \left[ {\matrix{ p & q \cr r & s \cr } } \right];B = \left[ {\matrix{ {{p^2} + {q^2}} & {pr + qs} \cr {pr + qs} & {{r^2} + {s^2}} \cr } } \right]$$ If the rank of matrix $$A$...

If the rank of a $$5x6$$ matrix $$Q$$ is $$4$$ then which one of the following statements is correct?

$$X = {\left[ {\matrix{ {{x_1}} & {{x_2}} & {.......\,{x_n}} \cr } } \right]^T}$$ is an $$n$$-tuple non- zero vector. The $$n\,\, \times \,\,n$$ matrix $$V = X{X^T}$$