Which one of the following removes temporary hardness of water?

If $m$ and $n$ are respectively the order and degree of the differential equation of the family of parabolas with origin as its focus and $X$-axis as its axis, then $mn-m+n=$

One thousand small water drops of equal radii combine to form a big drop. The ratio of final surface energy to the total initial surface energy is

Observe the following statements regarding the purification of bauxite:
$I$. During Hall's process,silica is removed as $Si$ (vapour).
$II$. Bauxite ore contaminated with $Fe_2O_3$ is purified in Baeyer's process.
$III$. During Serpeck's process,$AlN$ is formed.
The correct answer is:

Which one of the following statements is correct about biodiversity?

The end correction for the vibrations of air column in a tube of circular cross-section will be more if the tube is