Which of the following pairs is incorrect?

Identify $acetaldoxime$.

The differential equation obtained by eliminating the arbitrary constants $a$ and $b$ from $xy = ae^x + be^{-x}$ is

The angle between the line joining the points $(1, -2)$ and $(3, 2)$ and the line $x + 2y - 7 = 0$ is

On closing an open organ pipe from one end,it is noticed that the frequency of the third harmonic is $50 ~Hz$ more than the fundamental frequency of vibration in the open organ pipe. The fundamental frequency of the open organ pipe is (in $~Hz$)

$A$ gas at the temperature $250\, K$ is contained in a closed vessel. If the gas is heated through $1\, K$, then the percentage increase in its pressure will be .... $\%$