To answer the first question, we need to identify the missing note in the D minor chord. Given the image of the treble-clef staff with whole notes on D and A, we can determine the missing note by locating the third note of the D minor chord. In the case of D minor, the third note is F. Therefore, the missing note that completes the D minor chord is F natural, which is option B.
To answer the second question, we need to identify the note that is lowered in a major chord to create a minor chord. A major chord consists of the root note, the major third, and the perfect fifth. To create a minor chord, we lower the third note of the major chord by a half step. Therefore, the answer is option A - the third.
To answer the third question, we need to identify the correct note combination for an A minor chord. An A minor chord consists of the root note A, the minor third, and the perfect fifth. So, the correct note combination for an A minor chord would be A - C - E, which is option C.