**Core Concept**
Frenkel's exercise is a therapeutic technique used to treat certain cases of congenital dislocation of the hip (CDH) in infants. It involves a series of gentle manipulations and exercises to relocate the femoral head into the acetabulum.

**Why the Correct Answer is Right**
Frenkel's exercise is specifically indicated in infants with CDH, particularly those with a stable hip but a subluxable or dislocatable hip. The exercise involves gentle traction and manipulation to improve the hip's congruence and prevent further dislocation. This technique is often performed under general anesthesia and is usually done before the child is 6 months old.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because Frenkel's exercise is not typically used in cases of developmental dysplasia of the hip (DDH) in older children or adults.
* **Option B:** This option is incorrect because the Pavlik harness is a different orthotic device used to treat CDH in infants, but it is not the same as Frenkel's exercise.
* **Option C:** This option is incorrect because closed reduction is a different technique used to treat CDH in infants, but it is not the same as Frenkel's exercise.

**Clinical Pearl / High-Yield Fact**
Frenkel's exercise should be performed before the child is 6 months old to maximize the chances of successful treatment and prevent further dislocation.

**Correct Answer: C. Closed reduction.**