Final answer:
Fatty tissue is radiolucent and appears as areas of lower optical density on a mammogram, hence the correct answer to the question is A. radiolucent/lower. Mammograms utilize this property to differentiate between fatty and dense tissues, which is vital for detecting abnormalities such as tumors.
Step-by-step explanation:
Fatty tissue is generally radiolucent and is seen on the mammogram as areas of lower optical density. Thus the correct answer is A. radiolucent/lower. Breast tissue density is an important factor in mammographic imaging. Fatty tissue shows up as darker areas on a mammogram because it is less dense and absorbs fewer x-rays. In contrast, denser tissues such as glands and tumors are more radiopaque and appear as areas of higher optical density, showing up as whiter areas on a mammogram. This contrast is critical for early detection of breast cancer, as denser tissue could hide the presence of tumors. That's why mammography is sometimes complemented with MRI, which is not influenced by tissue density in the same way as x-rays and can therefore help in detecting abnormalities that might be obscured on a mammogram.