Which one of the following halogens liberates oxygen,when passed through hot concentrated $KOH$ solution?

If $f:[-6,6] \rightarrow R$ is defined by $f(x)=x^2-3$ for $x \in R$,then $(f \circ f \circ f)(-1)+(f \circ f \circ f)(0)+(f \circ f \circ f)(1)$ is equal to

The numbers $a_n = 6^n - 5n$ for $n = 1, 2, 3, \ldots$ when divided by $25$ leave the remainder:

The compound $CH_3-C(CH_3)=CH-CH_3$ on reaction with $NaIO_4$ in the presence of $KMnO_4$ gives :-

The solution of the equation $\cos^2 \theta + \sin \theta + 1 = 0$ lies in the interval

$\frac{12}{3 + \sqrt{5} - 2\sqrt{2}} = $