Given that,
- $\text{P}$
- $\text{Q}$
- $\text{R}$
- $\text{S}$
French is easier than Dutch; Chinese is harder than Japanese; Dutch is easier than Japanese, and Spanish is easier than French.
Using the above information we get, $\underbrace{{\color{Red}{\text{Chinese}}} > {\color{Magenta}{\text{Japanese}}}}_{{\color{orange}{\text{Most difficult pair of languages}}}} >{\color{Purple}{\text{Dutch}}}>{\color{Blue}{\text{French}}} > {\color{Green}{\text{Spanish}}}.$
$\therefore$ A girl $\text{Q}$ is learning the most difficult pair of languages.
Correct Answer $:\text{B}$