Which of the following criteria has to be satisfied for no tension at any point on a gravity dam?

• A. The resultant of all the forces must always pass through the mid-point of the base of the dam
• B. The resultant force for all conditions of loading must pass through the middle third of the base
• C. The resultant of all the forces must pass through the upstream extremity of the middle third of the base
• D. The resultant of all the forces must pass through the downstream extremity of the middle third of the base