Which one of the following is not a second messenger in hormone action?

Which one of the following molecules contains both ionic and covalent bonds?

$A$ light wave enters from medium $1$ to medium $2$. Its velocity in the $2^{nd}$ medium is double that of the $1^{st}$ medium. For total internal reflection to occur,the angle of incidence must be greater than which of the following values?

The number of moles of electrons required to deposit $36 \ g$ of $Al$ from an aqueous solution of $Al(NO_3)_3$ is (At. wt. of $Al = 27$)

$\lim _{x \rightarrow 0} \frac{\tan x - \sin x}{x^3}$ is equal to

$A$ line $L$ has intercepts $a$ and $b$ on the coordinate axes. When the coordinate axes are rotated through an angle $\alpha$ keeping the origin fixed,the same line $L$ has intercepts $p$ and $q$ on the new axes. Then