I believe the answer should be B
The A minor chord i7 is the A min 7 chord, and contains the notes A, C, E, and G. This tonic 7th chords root / starting note is the 1st note (or scale degree) of the A natural minor scale. The roman numeral for number 1 is 'i', and is used to indicate this is the 1st chord in the scale.
The diaphragm is another term for the aperture, so it controls the amount of light passing into the film camera.
