$CH_4$ diffuses two times faster than a gas $X$. The number of molecules present in $32 \ g$ of gas $X$ is ($N$ is Avogadro number).

If ${}^n C_{r-1}=330$,${}^n C_r=462$,and ${}^n C_{r+1}=462$,then $r$ is equal to

Which enzyme was targeted during the first clinical gene therapy given in $1990$ to a four-year-old girl?

Perhydrol is an aqueous solution of

The reading of the ammeter in the circuit shown will be: (in $A$)

$A$ whistle $S$ of frequency $f$ revolves in a circle of radius $R$ at a constant speed $v$. What is the ratio of the largest and smallest frequency detected by a detector $D$ at rest at a distance $2R$ from the center of the circle as shown in the figure? (Take $c$ as the speed of sound.)