The yield moment of a cross section is defined as the moment that will just produce the yield stress in A. The outer most fibre of the section B. The inner most fibre of the section C. The neutral fibre of the section D. The fibre everywhere

The correct answer is: A. The outer most fibre of the section.

The yield moment of a cross section is defined as the moment that will just produce the yield stress in the outer most fibre of the section. This is because the outer most fibre is the most highly stressed fibre in the section. The yield stress is the stress at which a material begins to deform plastically. When a material is subjected to a bending moment, the outer most fibre is in tension and the inner most fibre is in compression. The neutral fibre is the fibre that is neither in tension nor in compression. The yield moment is calculated by taking the product of the yield stress, the area of the cross section, and the distance from the neutral fibre to the outer most fibre.

Option B is incorrect because the inner most fibre is not the most highly stressed fibre in the section.

Option C is incorrect because the neutral fibre is neither in tension nor in compression.

Option D is incorrect because the fibre everywhere does not experience the same stress.