For very high frequencies, the effective impedance of the circuit (shown in the figure) will be :-

 

For very high frequency, $\mathrm{L\omega }$will be very high, so branch will not conduct current which has inductance; whereas, at high frequency, 
$\frac{1}{\mathrm{C\omega }}$will be very small, so effective reactance of the capacitor will be zero. So, from the given circuit, total impedance will be  $1+2=3 \mathrm{\Omega }$