The synonym for water gas when used in the production of methanol is

The decreasing order of nucleophilicity among the following nucleophiles is:
$(I)$ $CH_3-COO^-$
$(II)$ $CH_3-O^-$
$(III)$ $CH_3-CH_2^-$
$(IV)$ $CH_3-SO_3^-$

$(\tan ^{-1} x)^2+(\cot ^{-1} x)^2=\frac{5 \pi^2}{8} \Rightarrow x=$

Brush bordered epithelium is found in

In which of the following reactions,$H_2O_2$ acts as a reducing reagent?

The solution of $(x^2+y^2) dx = 2xy dy$ is: