Which one of the following combination of constants has dimensions of time? $[\mathrm{G}=$ constant of gravitation, $\mathrm{h}=$ Planck's constant, $\mathrm{c}=$ velocity of light $]$

• Correct answer
  A

  $\left[\frac{G h}{c^{5}}\right]^{\frac{1}{2}}$
• B

  $\left[\frac{G h}{c}\right]^{\frac{1}{2}}$
• C

  $\left[\frac{G h}{c^{4}}\right]^{\frac{1}{2}}$
• D

  $\left[\frac{G h}{c^{3}}\right]^{\frac{1}{2}}$

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