Which of the following substances combines with hemoglobin in the blood to form carboxyhemoglobin?

If $u=\sin ^{-1}\left(\frac{x^2+y^2}{x+y}\right)$ then $x \frac{\partial u}{\partial x}+y \frac{\partial u}{\partial y}$ is equal to:

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:

If the angles of a triangle are in the ratio $4:1:1,$ then the ratio of the longest side to the perimeter is

The glands present in the skin of frog are

The points with position vectors $60i + 3j$,$40i - 8j$,and $ai - 52j$ are collinear if $a = \dots$