Final answer:
Withdrawal symptoms like shaking indicate physical dependence on a substance, where the body reacts negatively when the substance use is stopped. This is distinct from psychological craving and relapse, which are related but separate aspects of addiction.
Step-by-step explanation:
Withdrawal symptoms such as shaking suggest that the person is experiencing physical dependence on a substance. Physical dependence occurs when the body adapts to a substance, leading to withdrawal symptoms upon cessation. These physical withdrawal symptoms can range from tremors, pain, seizures, and agitation. On the other hand, psychological craving is about the emotional need for a substance and can manifest as a strong desire or urge to use the substance. Tolerance is another related concept where increased amounts of the substance are required to achieve the same effect, indicating physiological dependence.
Relapse refers to returning to substance use after an attempt to stop. This is different from withdrawal, which is the body's response to the absence of the substance after a period of sustained use. Therefore, the most correct answer is that withdrawal symptoms suggest the person is experiencing withdrawal from a substance.