**Core Concept**
Chronic ulcerative colitis (CUC) is a type of inflammatory bowel disease (IBD) characterized by chronic inflammation and ulceration of the colonic mucosa. The treatment of CUC involves a combination of medications aimed at inducing and maintaining remission, managing symptoms, and preventing complications.

**Why the Correct Answer is Right**
The treatment of choice for chronic ulcerative colitis is aminosalicylates, specifically sulfasalazine or mesalamine. These medications work by inhibiting the production of pro-inflammatory cytokines and reducing inflammation in the colon. They are effective in inducing and maintaining remission in patients with mild to moderate CUC. Sulfasalazine and mesalamine act locally in the colon, reducing mucosal inflammation and preventing further damage.

**Why Each Wrong Option is Incorrect**
**Option A:** Steroids, such as prednisolone, are effective in inducing remission in CUC but are not the first-line treatment due to their side effects and the risk of corticosteroid dependence.
**Option B:** Immunomodulators, such as azathioprine, are used in patients with CUC who are refractory to aminosalicylates or have complications, but are not the initial treatment of choice.
**Option C:** Biologics, such as infliximab, are effective in patients with CUC who are refractory to conventional therapy, but are not the first-line treatment due to their cost and potential side effects.

**Clinical Pearl / High-Yield Fact**
Aminosalicylates, such as sulfasalazine and mesalamine, are effective in treating CUC due to their ability to reduce inflammation and prevent further damage to the colon mucosa.

**Correct Answer:** C.