Step 1: Decode fixed relations and genders.
Z is female; S is Z’s brother $\Rightarrow$ S is male.
X is sister of Y $\Rightarrow$ X, Y are females.
P is the father of Y $\Rightarrow$ P is male.
Y is the mother of R $\Rightarrow$ Y female, R child.
Let the husband of Z be one of the males.
Step 2: Start with the "Q and Z’s husband" condition.
"The husband of Z is second to the right of Q" and "Q sits between two males."
Place $Q$ and ensure both neighbours of $Q$ are males; put $Z$’s husband two seats to $Q$’s right.
Step 3: Use the S–mother and ‘daughter’ clues.
"S sits to the immediate left of his mother" $\Rightarrow$ the person to the right of $S$ is \emph{Z’s mother}.
"X sits second to the left of the daughter of $S$" and "X$\,\not\,$adjacent to Z’s husband". Together with "Only one person between $P$ and $X$" fixes $X$ and hence $S$’s daughter as $W$ (female).
Step 4: Complete the circle consistently.
A unique consistent arrangement (up to rotation) is:
\[
\boxed{P \;-\; Y \;-\; X \;-\; Z \;-\; W \;-\; S \;-\; Q \;-\; R \;-\; (back~to~P)}
\]
with all facing the centre, and \emph{$P$ is the husband of $Z$}.
Check all clues: $Q$ between two males $(S,R)$; Z’s husband ($P$) is second right of $Q$; $X$ is second left of $W$ (the daughter of $S$); $X$ is not adjacent to $P$; exactly one between $P$ and $X$; exactly one between $Z$ and $Y$; $Y$ not adjacent to $W$; $S$ is immediately left of his mother $Q$; exactly one between $Q$ (Z’s mother) and $W$. All satisfied.
Step 5: Evaluate the options.
(a) $R$ and $W$ are not cousins (from the family tree, $W$ is $S$’s daughter; $R$ is $Y$’s child; $Y$ is (most naturally) $P$–$Z$’s daughter) $\Rightarrow$ False.
\hspace*{0.8em}(\emph{Even without assuming mothers, the arrangement makes (a) not necessarily true.})
(b) From Step 4, the mother of $S$ and $Z$ is $Q$ $\Rightarrow$ True.
(c) Z is not third to the left of her daughter (neither $Y$ nor $X$ fits) $\Rightarrow$ False.
(d) $R$ has $Q$ (female) as one neighbour $\Rightarrow$ False.
Hence (b) is correct.