Which of the following statements is correct for optically active alkyl halides,upon reaction with nucleophiles?

	$S_{N}1$	$S_{N}2$
$(a)$	Retention of configuration	Inversion of configuration
$(b)$	Racemisation	Inversion of configuration
$(c)$	Inversion of configuration	Retention of configuration
$(d)$	Racemisation	Retention of configuration

In the above reaction,product $B$ is:

Differentiate between the $S_N2$ and $S_N1$ mechanisms of alkyl halides.

Match the reactions in List-$I$ with the features of their products in List-$II$ and choose the correct option.
| List-$I$ | List-$II$ |
| :--- | :--- |
| $(P)$ $(-)-1$-Bromo-$2$-ethylpentane $\xrightarrow{aq. NaOH, S_N2}$ | $(1)$ Inversion of configuration |
| $(Q)$ $(-)-2$-Bromopentane $\xrightarrow{aq. NaOH, S_N2}$ | $(2)$ Retention of configuration |
| $(R)$ $(-)-3$-Bromo-$3$-methylhexane $\xrightarrow{aq. NaOH, S_N1}$ | $(3)$ Mixture of enantiomers |
| $(S)$ $(3S, 5S)-5$-bromo-$3$-methylheptane $\xrightarrow{aq. NaOH, S_N1}$ | $(4)$ Mixture of structural isomers |
| | $(5)$ Mixture of diastereomers |

Which of the following halogens reacts explosively with alkanes?

Which is the major product expected from the following $S_{N}2$ reaction?