Consider the following groups:
$I$. $-OAc$
$II$. $-OMe$
$III$. $-OSO_2Me$
$IV$. $-OSO_2CF_3$
The order of leaving power is:

Which of the following compounds is optically inactive?

Identify $A$ and $B$ in the chemical reaction.

Which of the following reactions is an example of a nucleophilic substitution reaction?

Which of the following halogens reacts explosively with alkanes?

The mechanism of $S_{N}1$ reaction is given as:
$R-X$ $\rightarrow R^{\oplus} X^{\ominus}$ $\rightarrow R^{\oplus} | X^{\ominus}$ $\xrightarrow{Y^{\ominus}} R-Y + X^{\ominus}$
(Ion pair) (Solvent separated ion pair)
$A$ student writes general characteristics based on the given mechanism as:
$(a)$ The reaction is favoured by weak nucleophiles
$(b)$ $R^{\oplus}$ would be easily formed if the substituents are bulky
$(c)$ The reaction is accompanied by racemization
$(d)$ The reaction is favoured by non-polar solvents.
Which observations are correct?