Final answer:
Thicker body parts increase scatter and decrease contrast in x-ray imaging due to greater interaction with x-rays and a higher likelihood of scatter through the Compton effect.
Step-by-step explanation:
The thickness of a body part affects scatter and contrast during x-ray imaging. Thicker body parts have more material for x-rays to interact with, leading to a higher likelihood of scatter through the Compton effect. This increased scatter can diffuse the x-ray beam, reducing the sharpness of the resulting image. Consequently, as the body part thickness increases, scatter increases and image contrast decreases because there's less differentiation between the densities of different structures within the body part. Therefore, thicker body parts increase scatter and decrease contrast, which corresponds to option B in the given question.