If the pair of straight lines $xy-x-y+1=0$ and the line $ax+2y-3a=0$ are concurrent,then $a$ is equal to

The solution of the differential equation $\frac{dy}{dx} = \frac{xy+y}{xy+x}$ is

$\sqrt{12-\sqrt{68+48 \sqrt{2}}}$ is equal to :

Which of the following is the strongest Bronsted base?

Energy levels $A, B, C$ of a certain atom correspond to increasing values of energy, i.e., $E_A < E_B < E_C$. If $\lambda_1, \lambda_2, \lambda_3$ are the wavelengths of radiation corresponding to the transitions $C \to B$, $B \to A$, and $C \to A$ respectively, which of the following relations is correct?

Would you expect the second electron gain enthalpy of $O$ to be positive,more negative,or less negative than the first? Justify your answer.