Which of the following oxides does not form an acidic aqueous solution?

Who first discovered lichens?

Identify $A$ and $B$ in the following reaction:
$C_2H_5Cl \xrightarrow{A} C_2H_5OH \xleftarrow{B} C_2H_5Cl$

If the angle $2 \theta$ is acute,then the acute angle between the pair of straight lines $x^2(\cos \theta - \sin \theta) + 2xy \cos \theta + y^2(\cos \theta + \sin \theta) = 0$ is:

For a body moving in a circular path,what is the condition for no skidding if $\mu$ is the coefficient of friction?

The ratio between kinetic energy and the total energy of the electrons of a hydrogen atom according to Bohr's model is