Which function has an essential singularity at x=0x=0x=0?
f(x)=sinxf(x) = \sin xf(x)=sinx
f(x)=sinxxf(x) = \frac{\sin x}{x}f(x)=xsinx
f(x)=e1/xf(x) = e^{1/x}f(x)=e1/x
f(x)=1x2f(x) = \frac{1}{x^2}f(x)=x21