For beam design, the cross section dimensions of the beam are determined: A. Based on allowable normal stress, but the allowable shear stress should always be checked to be sure it is not exceeded. B. Based on the allowable shear stress, but the allowable normal stress should always be checked to be sure it is not exceeded. C. Such that both the allowable normal stress and the allowable shear stress are reached at the same time. D. Based on the allowable normal stress. E. The allowable shear stress is not an important design consideration.