Which among the following is $NOT$ a dicarboxylic acid?

Two identical metal plates show the photoelectric effect when light of wavelength ${\lambda _A}$ falls on plate $A$ and ${\lambda _B}$ falls on plate $B$,where ${\lambda _A} = 2{\lambda _B}$. The maximum kinetic energy is:

Which of the following is mismatched?

The excess pressure in a soap bubble is thrice that in another one. Then the ratio of their volumes is:

If $P=(0,1,2)$,$Q=(4,-2,1)$,and $O=(0,0,0)$,then $\angle POQ$ is equal to

Which of the following is a synthetic auxin?