Which one of the following is mainly responsible for the depletion of the ozone layer?

The period of $\sin ^4 x + \cos ^4 x$ is

The number of divisors of $7!$ is

The incentre of the triangle with vertices $(1, \sqrt{3})$,$(0, 0)$ and $(2, 0)$ is

$A$ source of sound is travelling with a velocity of $40\, km/h$ towards an observer and emits sound of frequency $2000\, Hz$. If the velocity of sound is $1220\, km/h$,what is the apparent frequency heard by the observer in $Hz$?

In the circuit shown in the figure,the potential difference across the $4.5\,\mu F$ capacitor is ....... $V$.