If f(x)=\int_{0}^{x} \frac{\sin t}{t} d t, x>0 then

f(x) has a local maxima at x=n \pi(n=2 k, k \in I^{+})

{f}( {x}) has a local minima at {x}= {n} \pi( {n}=2 {k}, {k} \in {I}^{+})

{f}( {x}) has neither maxima nor minima at {x}= {n} \pi( {n} \in {I}^{+})