The first human drug made by using genetic engineering technique was

If $\frac{x^2+x+1}{x^2+2x+1} = A + \frac{B}{x+1} + \frac{C}{(x+1)^2}$,then $A-B$ is equal to

The polar equation of the circle with centre $\left(2, \frac{\pi}{2}\right)$ and radius $3$ units is :

Two bodies $A$ and $B$ of equal mass are suspended from two separate massless springs of force constant $k_{1}$ and $k_{2}$ respectively. The bodies oscillate vertically such that their maximum velocities are equal. The ratio of the amplitudes of body $A$ to that of body $B$ is

Acetic acid is reacted with metallic sodium to form hydrogen and $X$. When $X$ is heated with sodalime,$Y$ and sodium carbonate are formed. $Y$ is

Arrange the following set of compounds in order of their decreasing relative reactivity with an electrophile,$E^{+}$:
$(a)$ Chlorobenzene,$2,4-$dinitrochlorobenzene,$p-$nitrochlorobenzene
$(b)$ Toluene,$p-CH_3-C_6H_4-NO_2$,$p-O_2N-C_6H_4-NO_2$