In the following sequence of reactions
$CH_3CH_2OH$ $\xrightarrow{P + I_2} A$ $\xrightarrow{Mg, \text{Ether}} B$ $\xrightarrow{HCHO} C$ $\xrightarrow{H_2O} D$
then compound $D$ is -

The most abundant prokaryotes helpful to humans in making curd from milk and in the production of antibiotics are the ones categorized as:

The polar equation $\cos \theta + 7 \sin \theta = \frac{1}{r}$ represents a

$A$ cell is connected between the points $A$ and $C$ of a circular conductor $ABCD$ of centre $O$ with angle $AOC = 60^{\circ}$. If $B_1$ and $B_2$ are the magnitudes of the magnetic fields at $O$ due to the currents in $ABC$ and $ADC$ respectively,the ratio $\frac{B_1}{B_2}$ is

If $\tan x + \tan \left(x + \frac{\pi}{3}\right) + \tan \left(x + \frac{2\pi}{3}\right) = 3$,then $\tan 3x$ is equal to

If a convex lens of focal length $80 \ cm$ and a concave lens of focal length $50 \ cm$ are combined together,what will be their resulting power?