Which of the Following Is an Improper Form of the Null

Which of the following is an improper form of the null and alternative hypotheses?

A) $H _ { 0 } : \mu \leq \mu _ { 0 }$ and $H _ { a } : \mu > \mu _ { 0 }$
B) $H _ { 0 } : \mu = \mu _ { 0 }$ and $H _ { a } : \mu \neq \mu _ { 0 }$
C) $H _ { 0 } : \mu < \mu _ { 0 }$ and $H _ { a } : \mu \geq \mu _ { 0 }$
D) $H _ { 0 } : \mu \geq \mu _ { 0 }$ and $H _ { a } : \mu < \mu _ { 0 }$