Two 10.0 m long iron rails are separated by 1.0 cm. The value of $\mathrm{\alpha }$ for iron is $1\times {10}^{-5}/\mathrm{C}°.$ If the initial temperature is $0°\mathrm{C}$, the temperature at which the rails will touch is 

• A

  $\text{50°C}$

• B

  $\text{100°C}$

• C

  $\text{200°C}$

• D

  $\text{10°C}$