The point of contraflexure is the point where

Answer: Option A

The point of contraflexure is the location on a beam where the bending moment (B.M.) changes its sign. This means that the bending moment transitions from positive to negative or vice versa at this point.

Key Points:
B.M. changes sign: The point of contraflexure is characterized by a change in the sign of the bending moment, indicating a shift in the direction of bending.

B.M. is maximum or minimum: Maximum or minimum bending moments occur at different points along the beam and are not necessarily at the point of contraflexure.

S.F. is zero: While shear force (S.F.) being zero might be a condition at some points, it is not a defining characteristic of the point of contraflexure. The point of contraflexure specifically involves a change in the bending moment direction.