Which of the following triads are called primary triads?

In music theory, the primary triads are the I, IV, and V chords in any key. These are called primary because they occur most frequently in music and form the basis of many harmonic progressions.

Here's how you can identify them:

1. Identify the key of the piece. The key tells you what the "I" chord is. For example, in the key of C major, the "I" chord is C.

2. The "IV" chord is the fourth note of the scale. In the key of C major, this would be F.

3. The "V" chord is the fifth note of the scale. In the key of C major, this would be G.

So, in the key of C major, the primary triads are C, F, and G. This will change depending on the key of the piece.