Answer:
G and B
Step-by-step explanation:
The tonic triad is built on the 1st degree of the scale corresponding to the key of the music, and consists of the 1st (root), 3rd, and 5th notes of that scale. In the key of G major, the tonic is G, so the tonic triad consists of the notes G, B and D.
The submediant triad is built on the 6th degree of the scale. In the key of G major, the 6th degree is E, so the submediant triad consists of the notes E, G, and B.
Therefore, in the key of G major, the tonic triad and the submediant triad both share the notes:
