The tonic of E flat major is E flat. Its dominant is B flat and its subdominant is A flat.
E-sharp.
The leading tone in the key of D, whether major or minor, is C#.
G sharp (enharmonic A flat).
The tonic of A is A.
leading tone
For bass clef, it is D. For treble clef, it is F. The way to remember what the dominant tone for any key is to count 4 notes above the 1st note. (the dominant is the 5th degree/note)
In ascending order, the names for each scale degree are the tonic, supertonic, mediant, subdominant, dominant, submediant, leading tone, and the tonic again.
Ascending up the major scale, the terms for each degree are the tonic, supertonic, mediant, subdominant, dominant, submediant, leading tone, and tonic again. The prefix "super" means above the tonic, and "sub" is below the tonic.
Tonic
leading tone
leading tone
Tonic
A harmonic minor scale in the key of E flat works best. For effect, go from the tonic chord to the submediant, than the supertonic, and then to the leading tone. Then do a subdominant chord, leading to the tonic with the dominant note played with the note a half-step above the dominant. It works if you want extra drama.
In the perspective of European-descendent theory, the degrees of any key or scale (major, minor, or modal) can be classified as follows: 1 - Tonic 2 - Supertonic 3 - Mediant 4 - Subdominant 5 - Dominant 6 - Submediant 7 - Leading Tone Let us take the case of C major as our key/scale: C - Tonic D - Supertonic E - Mediant F - Subdominant G - Dominant A - Submediant B - Leading Tone Similarily, this works in the minor keys, too. Using A natural harmonic as our key/scale: A - Tonic B - Supertonic C - Mediant D - Subdominant E - Dominant F - Submediant G - Leading Tone
The leading tone in a key is one half-step below the tonic. In the key of A major, the leading tone is G-sharp.
The leading tone is one half-step below the tonic, so in the key of B-flat the leading tone is A.