Check my answers, if i have a wrong answer tell me what the correct answer is

1. the triad is built on the second scale degree.
a. mediant
b. submediant (my answer)
c. supertonic
d. leading-tone

2. in a major key, the minor diatonic triads are
a. mediant, dominant, and submediant (my answer)
b. subdominant, dominant, and tonic
c. supertonic, subdominant, and dominant
d. supertonic, mediant, and submediant

3. in the key of c, the d-major chord is the
a. tonic (my answer)
b. subdominant
c. mediant
d. supertonic

4. the is the most stable-sounding diatonic triad.
a. tonic
b. subdominant (my answer)
c. mediant
d. supertonic

5. the sounds unstable because it is diminished.
a. supertonic (my answer)
b. subdominant
c. leading tone
d. submediant