Q: When someone is received under the Rite of Reception of Validly Baptized Christians into the Full Communion of the Catholic Church, must the candidate pronounce the Profession of Faith (“I believe and profess…”), or can it be simply “I do”, with the Profession of Faith in question-form (“Do you believe and profess…”)?
A: There is no provision for a Q/A here. The preparers of that ritual wanted it clear that the person was stepping forward of their own free will and making a declaration. I treated this on p. 63 of my book, When Other Christians Become Catholic.
Even so, it’s the priest’s words that make the person Catholic (“The Lord receives you…”). But the design is that the person makes a deliberate declaration of their belief first.