**Core Concept**
Ulcerative colitis (UC) is a type of inflammatory bowel disease (IBD) characterized by chronic inflammation and ulceration of the colonic mucosa. The emergency management of UC involves stabilizing the patient, managing symptoms, and preventing complications such as hemorrhage, perforation, and toxic megacolon.

**Why the Correct Answer is Right**
The correct answer is **B. Intravenous steroids**. Intravenous steroids, such as hydrocortisone, are the mainstay of emergency management in UC. They work by reducing inflammation and suppressing the immune response, thereby alleviating symptoms and preventing complications. The mechanism involves the inhibition of phospholipase A2, which is involved in the production of pro-inflammatory eicosanoids.

**Why Each Wrong Option is Incorrect**
**Option A:** Blood transfusions are not the primary treatment for UC, although they may be necessary in cases of significant blood loss.
**Option C:** Total parenteral nutrition (TPN) may be used in UC, but it is not the primary treatment for acute management.
**Option D:** Surgery is not typically considered an emergency management option for UC, unless there are complications such as perforation or hemorrhage.

**Clinical Pearl / High-Yield Fact**
Intravenous steroids should be initiated promptly in patients with moderate to severe UC, as they have been shown to reduce the risk of complications and improve outcomes.

**Correct Answer: B. Intravenous steroids**