12. 如圖(十)所示之梁ABCD,設B點的彎矩為M1,E點的彎矩為M2,若欲使M1+M2=0, 則B點及C點的間距s為何? (A) L/2(B) (2-√2)/L(C) √2L/2(D) (√2−1)/ L(E)送分