Final answer:
Loratadine (Claritin) is the best choice for the patient as it is a non-drowsy antihistamine and offers relief from seasonal rhinitis symptoms without causing sedation.
Step-by-step explanation:
The best choice for a patient who needs relief from the congestion of seasonal rhinitis but cannot afford to be drowsy before an important presentation would be c. Loratadine (Claritin). Loratadine is a non-drowsy antihistamine that is less likely to cause sedation compared to first-generation antihistamines like diphenhydramine (Benadryl) or hydroxyzine (Atarax). It acts by blocking the action of histamine that causes allergic symptoms, providing relief from nasal congestion, sneezing, and other allergy-related symptoms without causing drowsiness. Consulting a medical professional is recommended for long-term use, but for short-term relief, Loratadine is an effective choice.