**Core Concept**
Congenital ptosis is a condition where the eyelid droops due to a weak or underdeveloped levator muscle, which is responsible for eyelid elevation. In patients with congenital ptosis and good levator action, the goal of surgery is to improve eyelid function and appearance without compromising levator muscle function.

**Why the Correct Answer is Right**
Surgery of choice in this case is frontalis sling surgery. This procedure involves creating a sling from a strong, non-elastic material (such as a silicone strip) and attaching it to the frontalis muscle and the tarsal plate of the eyelid. When the frontalis muscle contracts, it pulls the eyelid upward, correcting the ptosis. This surgery is beneficial because it preserves the levator muscle function, allowing for natural eyelid movement and reducing the risk of complications.

**Why Each Wrong Option is Incorrect**
* **Option A:** Blepharoplasty is a surgical procedure used to correct eyelid sagging or excess skin, but it does not address the underlying muscle weakness in congenital ptosis.
* **Option B:** Müller's muscle resection is a surgical procedure used to correct ptosis in patients with poor levator action, but it is not the best option for patients with good levator action.
* **Option D:** Tarsal strip procedure is used to correct eyelid laxity, but it is not suitable for congenital ptosis with good levator action.

**Clinical Pearl / High-Yield Fact**
When evaluating a patient with congenital ptosis, it is essential to assess the levator muscle function to determine the best surgical approach. A levator function of 4-5 mm of elevation with the lid in the primary position is generally considered good levator action.

**Correct Answer: C. Frontalis sling surgery.**