........ of a reaction cannot be determined experimentally.

If $\frac{1-x+6x^2}{x-x^3} = \frac{A}{x} + \frac{B}{1-x} + \frac{C}{1+x}$,then $A$ is equal to

........ of a reaction cannot be determined experimentally.

When $FeCl_3$ reacts with $K_4[Fe(CN)_6]$,which of the following compounds is formed?

$A$ metal rod moves at a constant velocity in a direction perpendicular to its length. $A$ constant uniform magnetic field exists in space in a direction perpendicular to the rod as well as its velocity. Select the correct statement from the following:

Let $A = \{1, 2, \{3, 4\}, 5\}$. Which of the following statements is incorrect and why?
$\varnothing \in A$