In which of the folloiwng species the interatomic bond angle is $109^{\circ} 28^{\prime} ?$

• Correct answer
  A

  $\mathrm{NH}_3,\left(\mathrm{BF}_4\right)^{-1}$
• B

  $\left(\mathrm{NH}_4\right)^{+}, \mathrm{BF}_3$
• C

  $\mathrm{NH}_3, \mathrm{BF}_4$
• D

  $\left(\mathrm{NH}_2\right)^{-1}, \mathrm{BF}_3$

Hence, the correct answer is option: 'A'.