Bird flu is caused by

If $\frac{1}{2} \leq x \leq 1$,then $\cos ^{-1} x+\cos ^{-1}\left(\frac{x}{2}+\frac{1}{2} \sqrt{3-3 x^2}\right)$ is equal to

$Na_2S_2O_3$ reacts with moist $Cl_2$ to form $Na_2SO_4$,$HCl$ and $X$. Which one of the following is $X$?

In the following circuit,the equivalent resistance between $A$ and $B$ is ...... $\Omega$.

Two oxides of nitrogen,$NO$ and $NO_2$,react together at $253 \ K$ to form a compound of nitrogen $X$. $X$ reacts with water to yield another compound of nitrogen $Y$. The shape of the anion of $Y$ molecule is:

$\log _4 2 - \log _8 2 + \log _{16} 2 - \dots$ is equal to