2.设函数f(x)在区间 (-1,1) 内有定义,且 lim _(xarrow 0)f(x)=0, 则 ()-|||-A.当 lim _(xarrow 0)dfrac (f(x))(sqrt {|x|)}=0 f(x)在 x=0 处可导.-|||-B.当 lim _(xarrow 0)dfrac (f(x))(sqrt {{x)^2}}=0, f(x)在 x=0 处可导.-|||-C.当f(x)在 x=0 处可导时, lim _(xarrow 0)dfrac (f(x))(sqrt {|x|)}=0.-|||-D.当f(x)在 x=0 处可导时, lim _(xarrow 0)dfrac (f(x))(sqrt {{x)^2}}=0.