A/an is the interval between two pitches of the same name.
a. melody
b. interval
c. octave
d. whole step

changeable lenses of different focal lengths allows light to enter the camera,which then forms the image on light-sensitive film;

"prior to 1910, these new artists were called neo-impressionists, and they believed that "modern paris" was the proper subject for their paintings."

this is the text provided by the program, disregard other answers, as they are confusing and based on loose knowledge of the subject.   : )