Final answer:
Helen Frankenthaler's 'Mountains and Sea' is best described as c) Color field painting, due to its soak-stain technique and emphasis on large planes of uniform color.
Step-by-step explanation:
The description that relates best to Helen Frankenthaler's Mountains and Sea is c) Color field painting. This innovative abstract painting was created using a large canvas that she laid on the floor, employing what is known as the soak-stain technique. In 1952, she began using thinned oil paints to soak into an unprimed canvas, producing works with a translucent effect and negating the gestural brushwork associated with action painting. Frankenthaler's work emphasizes flat planes of color and an interest in the pure visual impact of color, separating her from action painters like Jackson Pollock and more in line with the intentions of the Color Field movement, which foregrounded large, uniform areas of color and a flat picture plane.