A pendulum clock loses 12 s a day if the temperature is ${40}^{\mathrm{o}}$ C and gains 4s a day if the temperature is ${20}^{\mathrm{o}}$ C. The temperature at which the clock will show correct time, and the co-efficient of linear expansion $\left(\mathrm{\alpha }\right)$ of the metal of the pendulum shaft are respectively:

• A

  ${30}^{\mathrm{o}}\mathrm{C};\mathrm{\alpha }=1.85\times {10}^{-3}$ / ${}^{\mathrm{o}}\mathrm{C}$
• B

  ${55}^{\mathrm{o}}\mathrm{C};\mathrm{\alpha }=1.85\times {10}^{-2}$ / ${}^{\mathrm{o}}\mathrm{C}$
• Correct answer
  C

  ${25}^{\mathrm{o}}\mathrm{C};\mathrm{\alpha }=1.85\times {10}^{-5}$ / ${}^{\mathrm{o}}\mathrm{C}$
• D

  ${60}^{\mathrm{o}}\mathrm{C};\mathrm{\alpha }=1.85\times {10}^{-4}$ / ${}^{\mathrm{o}}\mathrm{C}$

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