The answer to this question would be:a.1.2 cm
In this question, the length of the bridge is 25m, the coefficient of linear expansion is 12 × 10^-6/K and the change of temperature is 40K. Then the calculation of the changes of the length would be:
25m * 12 × 10^-6/K * 40K= 12,000*10^-6m * 10^2 cm/m= 1.2cm