13、单选-|||-L为抛物线 =(y)^2 ,(0leqslant yleqslant 1) 则积分 (int )_({L)_(2)}^2rd=dfrac ({(25))^2}({(d))^2}()-|||-(455)-|||-A .dfrac (1)(12)(5sqrt (5)-1) .-|||-B .(5sqrt (5)-1)-|||-C . dfrac (1)(12) .-|||-D .dfrac (1)(8)(5sqrt (5)-1)