Extracted text: Assuming concrete below the neutral axis to be cracked, the shear stress across the depth of a singly-reinforced rectangular beam section (a) increases parabolically to the neutral axis and then drops suddenly to zero value (b) increases parabolically to the neutral axis and then remains constant over the remaining depth (c) increases linearly to the neutral axis and then remains constant up to the tensioned steel. (d) increases parabolically to the neutral axis and then remains constant up to the tensioned steel.