8. Assertion : The bridges declared unsafe after a long use. Reason : Elastic strength of bridges losses with time.

(a)        If both assertion and reason are true and the reason is the correct explanation of the assertion.

(b)        If both assertion and reason are true but reason is not the correct explanation of the assertion.

(c)        If assertion is true but reason is false.

(d)        If the assertion and reason both are false.

(e)        If assertion is false but reason is true.

Explanation-

(a) A bridge during its use undergoes alternating strains for a large number of times each day, depending upon the movement of vehicles on it when a bridge is used for long time, it losses its elastic strength. Due to which the amount of strain in the bridge for a given stress will become large and ultimately, the bridge may collapse. This may not happen, if the bridges are declared unsafe after long use.

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