All of the above.
Each of the elements listed contributed to the development of the Baroque concerto:
- The newly emerging concept of major and minor tonality allowed for greater musical expression and complexity.
- The use of an active, ongoing bass line (often referred to as basso continuo) provided a harmonic foundation that was essential for the structure of Baroque music.
- The concertato principle, which involved dialogue and thematic exchanges between groups of musicians, was a defining characteristic of the concerto format.
Therefore, the correct response is "all of the above."