Which of the following is not produced during the electrolysis of brine solution?

Anoxygenic photosynthesis is characteristic of

The foci of the ellipse $\frac{x^2}{16} + \frac{y^2}{b^2} = 1$ and the hyperbola $\frac{x^2}{144} - \frac{y^2}{81} = \frac{1}{25}$ coincide. Then the value of $b^2$ is -

Choose the correct statement$(s)$:
$(A)$ The position of the centre of mass of a system is dependent on the choice of the coordinate system.
$(B)$ Newton's second law of motion is applicable to the centre of mass of the system.
$(C)$ Internal forces cannot change the state of the centre of mass.
$(D)$ Internal forces can change the state of the centre of mass.

The packing efficiency of the two-dimensional square unit cell shown below is ........... $ \% $

In the following circuit,the current flowing through the $1 \, k\Omega$ resistor is ..... $mA$.