A steel rod of length 1m is heated from  ${25}^{0}Cto{75}^{0}C$ keeping its length constant. The longitudinal strain developed in the rod is (Given : Coefficient of linear expansion of steel $=12\times {10}^{-6}{/}^{0}C$ )

• A

  $6\times {10}^6$

• B

  $-6\times {10}^{-5}$

• C

  $-6\times {10}^{-4}$

• D

  Zero