**Core Concept**
Asymmetric Moro's reflex at birth is a sign of hemispheric brain dysfunction, particularly indicating a problem with the motor control pathways of the affected hemisphere. This reflex is a normal response to a sudden loss of support, characterized by a symmetrical movement of the arms in a "M" shape, but in this case, it's asymmetrical.

**Why the Correct Answer is Right**
The asymmetric Moro's reflex is usually a sign of a perinatal brain injury that affects the motor cortex of the brain. This injury could be due to a variety of causes such as hypoxia-ischemia, trauma, or infection. The motor cortex of the brain is responsible for the voluntary movements of the limbs and face, and an injury to this area can lead to weakness or paralysis of the affected side. The asymmetric Moro's reflex is a sign of this weakness or paralysis, indicating that the motor control pathways of the affected hemisphere are not functioning properly.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because the asymmetric Moro's reflex is not a normal variant of the reflex, but rather a sign of an underlying neurological disorder.
* **Option B:** This option is incorrect because the asymmetric Moro's reflex is not a sign of a peripheral nervous system disorder, but rather a sign of a central nervous system disorder.
* **Option C:** This option is incorrect because while hypotonia can be a sign of a neurological disorder, it is not the only possible cause of an asymmetric Moro's reflex.

**Clinical Pearl / High-Yield Fact**
A key point to remember is that the asymmetric Moro's reflex is a sign of a hemispheric brain dysfunction, and it's essential to investigate the underlying cause of this reflex in a newborn. A thorough neurological examination, including assessment of tone, reflexes, and movement, is crucial in identifying the cause of this reflex.

**Correct Answer: B. Peripheral nervous system disorders.**