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 -

If $a = \hat{i} + 4 \hat{j}$,$b = 2 \hat{i} - 2 \hat{j}$,and $c = 5 \hat{i} + 9 \hat{j}$,then $c$ is equal to:

Consider the two following statements $A$ and $B$,and identify the correct choice given in the answers :
$(A)$ In photovoltaic cells the photoelectric current produced is not proportional to the intensity of incident light.
$(B)$ In gas-filled photoemissive cells,the velocity of photoelectrons depends on the wavelength of the incident radiation.

Which of the following substances is known as $Oil$ $of$ $Wintergreen$?

Which plant-derived latex is used as an alternative to rubber?

The angle between the lines whose direction cosines satisfy the equations $l+m+n=0$ and $l^2+m^2-n^2=0$ is