Lowercase Italic letter forms are primarily based on which shape?

The correct choice highlights that lowercase italic letter forms are primarily based on elliptically-curved shapes. This distinctive quality stems from the design principles that define italic typefaces, which are intended to convey a sense of elegance and fluidity.

Italic letters are characterized by their sloped designs and the way the curves are employed to create a more dynamic and flowing appearance, in contrast to the more rigid linear forms of regular typeface styles. The elliptically-curved shapes enhance readability and emotional expression, making them ideal for informal or expressive text. The rounded forms create a sense of movement and rhythm, which is essential in the art of calligraphy and type design. This is why the focus on elliptically-curved shapes accurately reflects the essence of lowercase italic lettering.