Hydrogen has three isotopes $\left(\mathrm{A}\right), \left(\mathrm{B}\right)$ and $\left(\mathrm{C}\right).$ If the number of neutron(s) in $\left(A\right), \left(B\right)$ and $\left(\mathrm{C}\right)$ respectively, are $\left(\mathrm{x}\right), \left(\mathrm{y}\right)$ and $\left(\mathrm{z}\right),$ the sum of $\left(\mathrm{x}\right), \left(\mathrm{y}\right)$ and $\left(\mathrm{z}\right)$ is

• Correct answer
  A

  $3$
• B

  $2$
• C

  $4$
• D

  $1$

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