What note completes the major triad with the root F
The note that completes the major triad with the root F is A.
To complete the major triad with the root F, we need to add two more notes: the third and the fifth.
A major triad consists of the root note, a major third interval (4 half steps above the root), and a perfect fifth interval (7 half steps above the root).
Since F is the root, the major third interval from F is A (which is 4 half steps above F), and the perfect fifth interval from F is C (which is 7 half steps above F).
Therefore, the note that completes the major triad with the root F is C.