The rate of the reaction, $\mathrm{A}+\mathrm{B}+\mathrm{C}\to$ Products, is given by

$\mathrm{r}=-\frac{\mathrm{d}\left[\mathrm{A}\right]}{\mathrm{d}\mathrm{t}}=\mathrm{k}\left[\mathrm{A}{]}^{\frac{1}{2}}\right[\mathrm{B}{]}^{\frac{1}{3}}[\mathrm{C}{]}^{\frac{1}{4}}$

The order of reaction is

• A

  1
• B

  2
• C

  $\frac{1}{2}$
• Correct answer
  D

  $\frac{13}{12}$

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