Place the following stages of pharmacokinetics in the correct order in which they occur in the body.

A. 8 hours: In 8 hours, four half-lives would have passed. Starting at 400 mg, the drug would decrease to 200 mg (2 hrs), 100 mg (4 hrs), 50 mg (6 hrs), and then 25 mg (8 hrs). At 8 hours, the level would be below 50 mg, not exactly 50 mg.

B. 4 hours: At 4 hours, two half-lives have passed. The concentration would decrease from 400 mg to 200 mg (2 hrs) and then to 100 mg (4 hrs). This is higher than the target concentration of 50 mg.

C. 6 hours: At 6 hours, three half-lives have passed. The drug concentration decreases from 400 mg to 200 mg (2 hrs), then to 100 mg (4 hrs), and finally to 50 mg (6 hrs). This matches the target level exactly.

D. 2 hours: After only one half-life, the concentration decreases from 400 mg to 200 mg. This is still much higher than 50 mg and does not reflect the correct timing for the required reduction.

A. Stimulates the immune system: Echinacea is most commonly used to enhance immune function and is often taken to reduce the severity or duration of colds and other respiratory infections. Its role in supporting immune activity makes this the most likely reason the patient is taking it.

B. Reduces acid reflux into esophagus: Acid reflux management is typically achieved with medications like proton pump inhibitors or lifestyle changes. Echinacea does not have therapeutic properties shown to reduce gastric acid or prevent reflux into the esophagus.

C. Improves memory loss in dementia: Herbs such as ginkgo biloba are sometimes used for cognitive support, but echinacea has not been shown to improve memory or slow the progression of dementia-related symptoms.

D. Improves oxygen exchange in the lungs: Lung oxygen exchange is enhanced by pulmonary medications such as bronchodilators or corticosteroids. Echinacea does not have properties that improve alveolar gas exchange.