Martha designed the model shown below to represent the positions of earth, sun, and moon during tides. the model most likely represents the positions of earth, sun, and moon when there is

 the model most likely represents the positions of earth, sun, and moon when there is: greatest difference between high and low tides
The high and low tides are created because of the combination of effects from the moon's gravitational forces with the sun's gravitational forces that affect the tide as the earth rotates