Which of the following is one of the first tools used for diagnosing issues due to illness or injury in an animal?

The physical exam is often considered one of the first tools used for diagnosing issues related to illness or injury in an animal. This hands-on assessment allows a veterinarian to evaluate various aspects of the animal's health by checking vital signs, examining the skin, ears, eyes, mouth, and other body systems for abnormalities. During a physical exam, the veterinarian can gather valuable information about the animal's condition, which can help formulate a diagnosis or decide on further diagnostic tests.

While other tools like ultrasound, radiographs, and blood tests are essential for specific situations, they are typically used after an initial physical examination has indicated that further evaluation is necessary. The physical exam serves as the foundational step in assessing an animal's health.