Which of the following elements has the highest reaction rate with water?

$X$ - In deep-sea hydrothermal vents,the average temperature is between $25^{\circ}C$ to $30^{\circ}C$.
$Y$ - Reptiles and amphibians are eurythermal.

In an $AC$ generator,a coil with $N$ turns,all of the same area $A$ and total resistance $R$,rotates with frequency $\omega$ in a magnetic field $B$. The maximum value of $emf$ generated in the coil is

Which of the following is the weakest reducing agent?

The number of unit cells present in $39 \ g$ of potassium if it crystallizes as body-centered cubic $(BCC)$ is ($N = \text{Avogadro number}$,$\text{At. wt. of potassium} = 39$).

At the same temperature and pressure,which of the following gases will have the highest kinetic energy per mole?