Gurvinder is a sixth$-$grade student who has to remember all the names of the Canadian prime ministers for his upcoming history exam. To facilitate his studying, he groups the prime ministers based on the first letter of their last names $($e$.$g$.,$ B$,$ M$,$ T$).$ What concept best captures Gurvinder's studying behaviour?

Clustering

None of these answers

Schemas$/$Scripts

Conceptual hierarchies