What is the triple point?

Is a negative value on the Kelvin scale possible? Why?

What does temperature measure? Write the $SI$ unit of temperature.

Two thermometers are used to record the temperature of a room. If the bulb of one is wrapped in a wet hanky,which of the following statements is correct?

Temperature of water at the surface of a lake is $ -20^{\circ}C$. Then,the temperature of water just below the lower surface of the ice layer is ...... $^{\circ}C$.

The electrical resistance in ohms of a certain thermometer varies with temperature according to the approximate law:
$R = R_{0} [1 + \alpha (T - T_{0})]$
The resistance is $101.6 \; \Omega$ at the triple-point of water $(273.16 \; K)$,and $165.5 \; \Omega$ at the normal melting point of lead $(600.5 \; K)$. What is the temperature (in $K$) when the resistance is $123.4 \; \Omega$?