Using the digits $0, 2, 4, 6, 8$ not more than once in any number,the number of $5$-digit numbers that can be formed is:

$A$ marine cartilaginous fish that can produce electric current is

An open vessel at $300 \ K$ is heated until $2/5$ of the air in it has been expelled. Assuming the volume of the vessel remains constant,find the temperature to which the vessel has been heated in $K$.

If $\sin {\theta _1} + \sin {\theta _2} + \sin {\theta _3} = 3,$ then $\cos {\theta _1} + \cos {\theta _2} + \cos {\theta _3} = $

In the given branch $AB$ of a circuit, a current $I = (10t + 5) \, A$ is flowing, where $t$ is time in seconds. At $t = 0$, the potential difference between points $A$ and $B$ $(V_A - V_B)$ is......$V$.

Secondary sewage treatment is mainly a