What is the correct expression for the form factor?

• A. Iᵣₘₛ * Iₐᵥ
• B. Iᵣₘₛ / Iₐᵥ
• C. Iᵣₘₛ + Iₐᵥ
• D. Iᵣₘₛ – Iₐᵥ