Observe the following molecules/ions. $\mathrm{NH}_4^{+}, \mathrm{NH}_3, \mathrm{BF}_3, \mathrm{OH}^{-}, \mathrm{CH}_3^{+}, \mathrm{H}^{+}, \mathrm{CO}, \mathrm{C}_2 \mathrm{H}_4$ The number of Lewis bases in the above list is

• A

  $2$
• B

  $3$
• Correct answer
  C

  $4$
• D

  $5$

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