a zygote is formed immediately after fertilization & fertilization is a stage in the sexual reproduction process ->  if a zygote is formed then a sexual reproduction process has happened  if a zygote is formed then a sexual reproduction process has happened & a student observes the formation of zygotes by one of the protists ->  a sexual reproduction process has happened in the protists that the student observed  volvox is a kind of protist & volvox reproduces sexually ->  volvox is a kind of protist that reproduces sexually  a sexual reproduction process has happened in the protists that the student observed & volvox is a kind of protist that reproduces sexually -> the protist may be volvox