Maximum density of $H_2O$ is at temperature

Assertion $(A)$: Rapidly changing temperatures can be measured by thermocouples.
Reason $(R)$: The thermal capacity of the junction of a thermocouple is very small.

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 ...... $^{\circ}C$.

$A$ Celsius and a Fahrenheit thermometer are dipped in boiling water. The temperature of water is lowered until the Fahrenheit thermometer shows $140^{\circ}F$. What is the fall in temperature on the Celsius thermometer (in $^{\circ}C$)?

The triple point of water is

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 $123.4 \; \Omega$?