**Question:** All of the following are characteristics of malignant tumors, except:

A. Increased cell division
B. Ability to invade nearby tissues
C. Ability to form blood vessels (angiogenesis)
D. Ability to form spread to distant sites (metastasis)

**Correct Answer: **C. Ability to form blood vessels (angiogenesis)**

**Core Concept:** Malignant tumors are characterized by uncontrolled cell division, invasion of nearby tissues, and the ability to form blood vessels (angiogenesis) as well as spread to distant sites (metastasis). Angiogenesis is the formation of new blood vessels from pre-existing ones, which is essential for supplying nutrients and oxygen to rapidly growing tumors.

**Why the Correct Answer is Right:** The correct answer, **C. Ability to form blood vessels (angiogenesis)**, is right because angiogenesis is a crucial process for supporting the growth of benign tumors (neither benign nor malignant tumors can form blood vessels themselves). Benign tumors grow slowly and do not require angiogenesis for growth and survival. Malignant tumors, however, require angiogenesis for rapid growth, invasion, and survival.

**Why Each Wrong Option is Incorrect:**

A. **Increased cell division (Option A)** is correct because malignant tumors exhibit increased cell division, which contributes to their uncontrolled growth and progression.

B. **Ability to form spread to distant sites (metastasis)** is correct because malignant tumors have the capacity to spread to distant organs, a process called **metastasis**. This is a defining characteristic of malignant tumors and contributes to their life-threatening potential.

D. **Ability to form spread to distant sites (metastasis)** is incorrect because, as mentioned above, this is a characteristic of malignant tumors and not a distinguishing factor between benign and malignant tumors.

**Why the Correct Answer is Right**:

Malignant tumors require angiogenesis for growth, invasion, and survival, while benign tumors grow slowly and do not require angiogenesis. Benign tumors can be managed surgically or with other non-invasive techniques without posing a significant threat to the patient's life. In contrast, malignant tumors can invade surrounding tissues, spread to distant organs, and potentially cause life-threatening complications.

**Why Each Wrong Option is Incorrect**:

A. Increased cell division (Option A) is incorrect because this feature is shared by both benign and malignant tumors, making it insufficient for distinguishing between them.

B. Ability to form spread to distant sites (Option B) is incorrect because this feature is also shared by malignant tumors.

C. Ability to form blood vessels (angiogenesis) (Option C) is incorrect because this feature is specific to malignant tumors and is not a defining characteristic of benign tumors. Benign tumors can grow large but do not require angiogenesis for their survival and growth.