Which of the following does not produce $NO_2$ gas with concentrated $HNO_3$?

Let $2 \sin^2 x + 3 \sin x - 2 > 0$ and $x^2 - x - 2 < 0$. ($x$ is measured in radians). The $x$ lies in the interval

Choanocytes are present in

The reaction of ethyl methyl ketone with $Cl_2$ in the presence of excess $OH^-$ gives the following major product:

Identify the organism shown in the given figure.

In the given figure,a ring of mass $m$ is kept on a horizontal surface,while a body of equal mass $m$ is attached through a string wound on the ring. When the system is released,the ring rolls without slipping. Consider the following statements and choose the correct option.
$(i)$ Acceleration of the centre of mass of the ring is $g/3$.
$(ii)$ Acceleration of the hanging particle is $2g/3$.
$(iii)$ Frictional force (on the ring) acts along the forward direction.
$(iv)$ Frictional force (on the ring) acts along the backward direction.