Which type of music is a secular musical form of the medieval era?

gregorian chant
estampie
plainchant
a cappella

Plainchant is a kind of music that is  secular medieval musical form

Explanation:

Plainchant is a kind of music that is  secular medieval musical form

Medieval music was written and developed for several different musical forms for a certain voice or instrumental songs. Medieval time  music developed for the religious and spiritual use of church. The liturgical genre primarily Gregorian chant, was monophonic in early mediaeval period.

answer; i believe the correct answer is "he who gladly serves"