Which of the following assessments primarily focuses on detecting temperature and swelling of tissues?

The assessment that primarily focuses on detecting temperature and swelling of tissues is palpation. This hands-on technique allows an examiner to assess various physical properties of a patient's tissues, including their temperature, texture, and whether there is any swelling or edema present. When a practitioner palpates an area, they can feel differences in temperature, which might indicate inflammation or infection, and they can also identify enlarged or swollen tissues that may suggest injury or pathology.

Other methods listed, such as percussion and auscultation, serve different purposes. Percussion involves tapping on the body to assess internal structures and can indicate things like fluid presence or organ size but does not directly measure temperature or swelling. Imaging techniques, such as X-rays or MRIs, provide visual representations of internal structures but do not allow for tactile assessment of temperature or swelling. Hence, palpation is the key technique for these specific concerns.