Consider the following statements for a beam based on theory of bending

1. Strain developed in any fibre is directly proportional to the distance of fibre from neutral surface

2. For flexural loading and linearly elastic action the neutral axis passes through the centroid of cross section 

3. The assumption of the plane cross sections remaining plane will not hold good during inelastic action

4. Instances in which the neutral axis does not pass through the centroid of a cross section include a homogenous

    symmetrical beam (with respect to neutral axis) and subjected to inelastic action. 

    Which of the statements given above are correct?