1. The problem states that a psychologist assessed 120 patients and 1/4 of them were diagnosed with anxiety disorder. 2. To find how many patients had anxiety disorder, we use the formula: $$\text{Number of patients with anxiety} = \frac{1}{4} \times 120$$ 3. Multiply 120 by 1/4: $$\frac{1}{4} \times 120 = \frac{120}{4} = 30$$ 4. Therefore, 30 patients were diagnosed with anxiety disorder. The correct answer is C. 30