Directions: Choose the right one from the four choices marked A, B, C or D. Chemically induced colon carcinogenesis in rodents is also suppressed by _____ of NSAIDs.
【单选题】设细长压杆的下端固定,上端可沿水平和垂直方向产生位移,但不能转动,杆件在失稳前和失稳后的形状如图,则下列结论中正确的是______。 (1)杆件失稳时,支座B处支反力偶矩M B 的方向为逆时针; (2)杆件失稳时,支座A处支反力偶矩M A 的方向为逆时针; (3)支反力偶矩M A 与M B 的值相等,即M A =M B ; (4)杆件中央截面上弯矩为零