Consider a model of finite control volume (volume V and surface area) fixed in space with elemental volume dV, vector elemental surface area d ( vec{S} ), density and flow velocity ( vec{V} ). ( rho vec{V}.d vec{S} ) is positive when _____________

• A. The mass flow is outward
• B. The mass flow is inward
• C. The mass flow is positive
• D. The mass flow is negative