Explanation: The diagnostic criteria for acne vulgaris typically include the identification of both comedones (blackheads and whiteheads) and inflammatory lesions (papules, pustules, nodules, and cysts). These manifestations are characteristic of acne vulgaris and help distinguish it from other skin conditions.

Incorrect choices: a. Scalp lesions - Scalp lesions are not specific to acne vulgaris and may be associated with other skin conditions or scalp disorders.

b. Yellowish-brown nodules - Yellowish-brown nodules are not commonly associated with acne vulgaris. These nodules may indicate a different skin condition.

c. Erythematous plaques with silver scales - This description is characteristic of psoriasis, a chronic autoimmune skin condition, and is not indicative of acne vulgaris.