已知有向光滑曲线 :x=varphi (t) ,=varphi (t)(aleqslant tleqslant beta ) 的始点B对应的参数值为α,-|||-终点A对应的参数值为β,则 (int )_(1)^f(x,y)dx= () .-|||-(A)∫8/x [φ(t),ϕ(t)]dt; (B)∫af [φ(t), (1)(t)] dt =-|||-(C) (int )_(alpha )^beta f[ varphi (t),varphi (t)] varphi '(t)dt ; (D) (int )_(beta )^alpha f[ varphi (t),psi (t)] varphi '(t)dt .