**Core Concept**
The question requires knowledge of the pathophysiology of gastrointestinal disorders, specifically the relationship between certain conditions and their characteristic symptoms. Painless diarrhea is a distinctive symptom that can help narrow down the differential diagnosis.

**Why the Correct Answer is Right**
Painless diarrhea is often associated with conditions where the intestinal mucosa is not significantly inflamed, such as in the case of lactose intolerance. This condition occurs due to the inability to digest lactose, a sugar found in milk, leading to its fermentation by colonic bacteria. The fermentation process produces gas, which is responsible for the diarrhea. Another condition that can cause painless diarrhea is bile salt malabsorption, which occurs when there is an excessive amount of bile salts in the colon, drawing water into the lumen and causing diarrhea.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is not provided.
**Option B:** This option is not provided.
**Option C:** This option is not provided.
**Option D:** This option is not provided.

**Clinical Pearl / High-Yield Fact**
It is essential to note that painless diarrhea can be a symptom of celiac disease, a chronic autoimmune disorder that causes the small intestine to react to gluten. Patients with celiac disease may present with diarrhea, abdominal pain, and weight loss, among other symptoms.

**Correct Answer:** **Lactose intolerance is a common cause of painless diarrhea.**