The SI unit for measuring absorbed dose is the:

The correct answer is the Gray (Gy), which is the SI unit used for measuring absorbed dose. The absorbed dose quantifies the energy deposited by ionizing radiation in a material, typically expressed in joules per kilogram. One gray is equivalent to one joule of radiation energy absorbed per kilogram of matter. This unit is essential in radiology and radiation therapy to assess how much radiation tissue absorbs, which helps in evaluating potential biological effects and guiding treatment options.

In contrast, the rad, rem, and sievert are older or different units related to radiation measurement. The rad is a non-SI unit that was historically used to measure absorbed dose, while the rem is a unit that measures the biological effect of ionizing radiation by taking into account the type of radiation and its impact on the tissue. The sievert is a unit used to measure the equivalent dose, which also accounts for biological effects. While these units are still encountered, the gray is the standard SI unit that is currently favored in scientific and medical contexts for absorbed dose measurement.