Though there be a million claimants,
... there is only one ("the"; definite article) "True Church", being "... the house of God, which is the church of the living God, the pillar and ground of the truth." (1 Timothy 3:15).
It is identified by scripture (Revelation 12).
It is called "the remnant" (Revelation 12:17), which is made known by the events in the earth (Acts 2:16-20), and of the heavens in Sun and Moon (Joel 2:28-32).
It is said to "keep the commandments of God" (Revelation 12:17, 14:12).
It keeps "the sabbath" (the 7th day) of the 4th commandment (Luke 23:54,56; Acts 1:2, 4:24, 13:14,27,42,44, 14:15-16, 15:21, 16:13, 17:2,24, 18:4; Hebrews 4:1-13; Revelation 1:10, 10:6, 14:7,12) in fulfillment of duty and prophecy (Isaiah 56:1-8; Acts 15:16-18; Amos 9:11-12).
It is said to have "the testimony of Jesus Christ" (Revelation 12:17), which is "the spirit of prophecy" (Revelation 19:10).
It is said to have "the faith of Jesus Christ" (Revelation 14:12).
It is visible (Colossians 1:16; 1 Corinthians 11:9; Ephesians 2:10).
It is knowable (2 Corinthians 3:2).
It is structural specific (Acts 15:22-23).
It is gift specific (Psalms 68:18; 1 Corinthians 12-14; Ephesians 4:8-16; Hebrews 5:1).
It is doctrinal specific (Acts 2:42), and such example is that it believes that king David is dead, buried, and not in Heaven, but sleeps in the grave (Acts 2:29,34, 13:36), and not nebulous, warning of false doctrine (2 Peter 2:1; Revelation 2:15), and false practices (Revelation 2:6).
It is "one faith" (Ephesians 4:5), not 'many' (Matthew 7:13b).
It is "one fold" (John 10:16; Isaiah 56:8) to which persons are "called" into (Galatians 1:6; 1 Peter 2:9), not 'many', to which persons are called "out" of (Revelation 18:4).
It is present to this very day, as Jesus has said, "... my church; and the gates of hell shall not prevail against it." (Matthew 16:18)
It "follows the Lamb withersoever he goeth" (Revelation 14:4), for his "way ... is in the sanctuary" (Psalms 77:13; Hebrews; Revelation).