Final answer:
The next best step in the management of this patient is surgery. The patient's symptoms are suggestive of intussusception, and surgical intervention is the preferred treatment.
Option C.
Step-by-step explanation:
The next best step in the management of this patient is C. Surgery.
The patient's symptoms, such as intense screaming and crying, abdominal mass, and the presence of a purplish-colored slimy stool, are suggestive of intussusception.
Intussusception occurs when one part of the intestine slides into another part, causing a blockage.
Surgical intervention, specifically an air enema or resection of the affected segment, is the preferred treatment for intussusception in infants.