It is interesting in the extreme that nobody has mentioned the Nicene Creed in this thread. The Nicene Creed is the definitive answer to this question, as determined by the people most interested in the matter.
Consider...
The Nicene Creed
We believe in one
God,
the Father almighty,
maker of heaven and earth,
of all things visible and invisible.
And in one Lord Jesus Christ,
the only Son of God,
begotten from the Father before all ages,
God from God,
Light from Light,
true God from true God,
begotten, not made;
of the same essence as the Father.
Through him all things were made.
For us and for our salvation
he came down from heaven;
he became incarnate by the Holy Spirit and the virgin Mary,
and was made human.
He was crucified for us under Pontius Pilate;
he suffered and was buried.
The third day he rose again, according to the Scriptures.
He ascended to heaven
and is seated at the right hand of the Father.
He will come again with glory
to judge the living and the dead.
His kingdom will never end.
And we believe in the Holy Spirit,
the Lord, the giver of life.
He proceeds from the Father and the Son,
and with the Father and the Son is worshiped and glorified.
He spoke through the prophets.
We believe in one holy catholic and apostolic church.
We affirm one baptism for the forgiveness of sins.
We look forward to the resurrection of the dead,
and to life in the world to come.
But this thread also illustrates the folly of Protestantism, which is based on the notion that we humans can read the Scriptures and decide for ourselves what they mean, regardless of the fact that our forefathers have studied and pondered these questions for millennia and have figured it out.
There is only one true church, and it is based in Rome. It isn't perfect; no human institution is, but it is the one true church.