Romans 1:19

19 since what may be known about God is plain to them, because God has made it plain to them.

Read Romans 1:19 Using Other Translations

Because that which may be known of God is manifest in them; for God hath shewed it unto them.
For what can be known about God is plain to them, because God has shown it to them.
They know the truth about God because he has made it obvious to them.