Which of the following is the most stable ecosystem?

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

Ionisation of which of the following will be maximum in water?

Which one of the following statements is not correct?

The wavelength of radiation emitted is $\lambda_0$ when an electron jumps from the third to the second orbit of a hydrogen atom. For the electron to jump from the fourth to the second orbit of the hydrogen atom,the wavelength of radiation emitted will be

Which one of the following correctly represents the variation of electronegativity $(EN)$ with atomic number $(Z)$ of group $13$ elements?