Identify the symmetrical ketone from the following compounds.

The Clemmensen reduction of acetone yields

In the following reactions,$P, Q, R$,and $S$ are the major products.
The correct statement$(s)$ about $P, Q, R$,and $S$ is(are):
$(A)$ Both $P$ and $Q$ have asymmetric carbon$(s)$.
$(B)$ Both $Q$ and $R$ have asymmetric carbon$(s)$.
$(C)$ Both $P$ and $R$ have asymmetric carbon$(s)$.
$(D)$ $P$ has asymmetric carbon$(s)$,$S$ does not have any asymmetric carbon.

$A$ and $B$ are isomers; Isomer $B$ is

The major product ‘$A$’ in the given reaction is:
$\text{Benzaldehyde} + \text{Acetophenone} \xrightarrow[293 \text{ K}]{OH^-} \text{'A' (Major product)}$

Which of the following compounds is the least reactive towards nucleophilic addition reactions?