Design of a member for strength is based on selecting an ( ) that will enable it to safely support its intended load. Since there are many unknown factors that can influence the actual stress in a member, then depending upon the intended use of the member, ( ) is applied to obtain the ( ) the member can support.
A．allowable stress, a factor of safety, allowable load B．allowable force, a factor of safety, allowable load C．allowable force, a factor, allowable load D．allowable stress, a factor, allowable load