| 19 × | biology | 4 × | botany | 1 × | taxonomy | ||
| 15 × | chemistry | 4 × | java | 1 × | music | ||
| 14 × | spelling | 4 × | geography | 1 × | physics | ||
| 13 × | english | 2 × | accounting | 1 × | nodejs | ||
| 11 × | medicine | 2 × | symbols | 1 × | shopping | ||
| 8 × | anatomy | 2 × | javascript | 1 × | database | ||
| 7 × | programming | 2 × | mnemonic | ||||
| 7 × | periodic-table | 1 × | humanbody | ||||
| 6 × | mathematics | 1 × | dates | ||||
| 5 × | elements | 1 × | interviews |