下列使用第二类换元法求积分无误的是 () [上册第-|||-27讲]-|||-A| int dfrac (1)(sqrt {{x)^2+1}}dxunderline ( )=lim _(xarrow +infty )f(xi et)-|||-B int dfrac (sqrt {{x)^2-1}}({x)^4}dx=dfrac (1)(t)-int tsqrt (1-{t)^2}dt-|||-C (int )_(1)^4dfrac (1)(1+sqrt {x)}dxunderline ( x)(e)^x=(t)^2 (int )_(1)^2dfrac (1)(1+t)dt-|||-D (int )_(0)^1(x)^2sqrt (1-{x)^2}dx arctan =(int )_(0)^1(int )_(0)^1(sin )^2t(cos )^2tdx