There are $3$ possible cases :-
$(1)$ $P$ is right, $Q$ and $R$ are wrong
It means $P$'s statement "S has at least $3$ cars" is true and $R$'s statement "S has at least one car" is false which means $S$ has actually less than one car which is contradicting $P$'s statement that $S$ has at least $3$ cars. So, It is NOT a possible case.
$(2)$ $R$ is right, $P$ and $Q$ are wrong
It means $P$'s statement "S has at least $3$ cars" is false. So, $S$ actually has less than $3$ cars. Now, Q's statement "S has less than 3 cars" is also false which means $S$ has actually at least $3$ cars. Both statements are contradicting each other. So, It is NOT a possible case.
$(3)$ $Q$ is right, $P$ and $R$ are wrong
It means $Q$'s statement "S has less than $3$ cars" is true and $P$'s statement "S has at least $3$ cars" is false which means $S$ has actually less than $3$ cars. $R$'s statement "S has at least one car" is also false which means $S$ has actually less than $1$ car. All $3$ statements are not contradicting each other. So, It is a possible case. Since, all $3$ statements are true. So, we can conclude from all the $3$ statements that "$S$ has less than $1$ car" (or) "$S$ has no car".
So, Answer is $(A)$