If dichloromethane $(DCM)$ and water $(H_2O)$ are used for differential extraction,which one of the following statements is correct?

What is the difference between distillation,distillation under reduced pressure,and steam distillation?

In the differential extraction method using a separating funnel,two layers are formed. What is the difference in the mixture before shaking the solution and at the end of the process?

Match column $-I$ and column $-II$ with the correct relation:

Column $-I$	Column $-II$
$(i)$ Liquid boiled at low temperature	$(a)$ Fractional distillation
$(ii)$ Glycerol from lye	$(b)$ Simple distillation
$(iii)$ The liquid with lower boiling point condenses first	$(c)$ Steam distillation
$(iv)$ The liquid with higher boiling point condenses first	$(d)$ Distillation under reduced pressure

On heating,some solid substances change from solid to vapour state without passing through liquid state. The technique used for the purification of such solid substances based on the above principle is known as

Fill in the blanks:
$1$. In formulas and reactions,the electron pair displacement is indicated by a curved arrow,and the single electron displacement is indicated by a ..........
$2$. There are more than .......... plates in the columns of fractional distillation.
$3$. Fractional distillation is used for the separation of liquids with a .......... difference in boiling points,and simple distillation is used for the separation of liquids with a .......... difference in boiling points.
$4$. The .......... technique is applied to separate different fractions of crude oil in petroleum.