A 50-year-old female patient presented with chief complaints of painless thyroid nodule. Fuher examination is insignificant. TSH levels are normal. FNAC reveals papillary changes with nuclear atypia. Total thyroidectomy is planned. However, during surgery, a nearby nerve is injured while ligating Superior thyroidal aery. Which of the following laryngeal muscle is likely to be affected?

Marked structures are as follows: a- Posterior cricoarytenoid b- Thyroarytenoid c- Cricothyroid d- Oblique interarytenoid The external branch of the superior laryngeal nerve is most likely to be injured during ligation of Superior thyroid aery because both of them course together in a neurovascular bundle near the superior lobe of thyroid gland. The only laryngeal muscle supplied by the external branch of superior laryngeal nerve is Cricothyroid.