Which of the following temperature measuring instruments need not touch the object whose temperature is being measured?

The root locus plot of the roots of the characteristics equation of a closed loop system having the open loop transfer function $$\frac{{{\text{K}}\left( {{\text{s}} + 1} \right)}}{{2\left( {2{\text{s}} + 1} \right)\left( {3{\text{s}} + 1} \right)}}$$    will have a definite number of loci for variation of K from 0 to $$\infty $$. The number of loci is

Phase lag of the frequency response of a second order system to a sinusoidal forcing function

Which of the following is not classified as a thermo electric pyrometer?

The temperature of tempering oil baths maintained at 400°C during heat treatment of steel is measured by a/an __________ thermocouple.