Which pronouns for “what” distinguish Shtokavian, Chakavian, and Kajkavian dialects?

The three main dialect groups of the Bosnian-Croatian-Montenegrin-Serbian language are named after the specific interrogative pronoun used for "what" in each respective dialect. These pronouns serve as a primary linguistic marker for distinguishing the groups:12

• Shtokavian: Uses the form što (or šta) for "what". This dialect is spoken across the entirety of Serbia, Montenegro, and Bosnia and Herzegovina, as well as inland Croatia.12
• Chakavian: Uses the form ča for "what". This dialect is primarily found along the Croatian seacoast, in Istria, and on various Adriatic islands.12
• Kajkavian: Uses the form kaj for "what". This dialect is spoken in northwestern Croatia, particularly in the region surrounding the capital, Zagreb.12

While these pronouns are the namesake for each group, the dialects also exhibit significant differences in their vowels, consonants, word forms, and overall vocabulary.1