Which of the following is an example of a Gram-positive bacterium?

Which of the following is an oxidizing agent?

Which of the following statements is not correct?

The strongest Bronsted base among the following anions is:

The angle between the lines whose direction cosines are given by the equations $l^2+m^2-n^2=0$ and $l+m+n=0$ is

$A$ double slit experiment is immersed in water of refractive index $1.33$. The slit separation is $1 ~mm$ and the distance between the slit and the screen is $1.33 ~m$. The slits are illuminated by light of wavelength $6300 ~Å$. The fringe width is: