Final answer:
For a patient experiencing a tonic-clonic seizure, the nurse should loosen restrictive clothing to ensure comfort and prevent breathing restrictions. Inserting a tongue blade and restraining the patient are contraindicated and may cause harm.
Step-by-step explanation:
The nurse caring for a patient experiencing a tonic-clonic seizure should prioritize patient safety and comfort without interfering with the seizure. The correct action to take is D. Loosen restrictive clothing. This helps to prevent any additional discomfort and ensures that the patient does not experience restricted breathing. Options A (insert padded tongue blade) and C (restrain the patient) are contraindicated as they may cause injury to the patient or worsen the seizure. Option B (apply oxygen) may be considered if the patient has difficulty breathing after the seizure or as per institutional protocols but is not a primary action during an active seizure.