Which of the following statements about tumors is true?

• A. Benign tumors do not invade surrounding tissues.
• B. Tumors are always caused by viral infections.
• C. All tumors are cancerous.
• D. Malignant tumors cannot spread to other parts of the body.

Answer: (A)

Verified step by step guidance

1. Understand the key terms: A tumor is an abnormal growth of cells. Tumors can be classified as benign (non-cancerous) or malignant (cancerous). Malignant tumors have the ability to invade surrounding tissues and spread to other parts of the body (metastasis).
2. Analyze the first statement: 'Benign tumors do not invade surrounding tissues.' This is correct because benign tumors are localized and do not spread or invade other tissues.
3. Analyze the second statement: 'Tumors are always caused by viral infections.' This is incorrect because tumors can arise from various causes, including genetic mutations, environmental factors, and sometimes viral infections, but not always.
4. Analyze the third statement: 'All tumors are cancerous.' This is incorrect because benign tumors are not cancerous, while malignant tumors are.
5. Analyze the fourth statement: 'Malignant tumors cannot spread to other parts of the body.' This is incorrect because malignant tumors are defined by their ability to invade surrounding tissues and metastasize to distant sites.