What is malignant?

• A. Not harmful in effect.
• B. Cancerous or capable of spreading.
• C. A condition of rapid heartbeat.
• D. An infectious disease.

Answer: (B)

Malignant means dangerous and capable of spreading, especially about tumors. In medical terms, a malignant tumor is cancerous and can invade nearby tissues and spread (metastasize) to distant parts of the body. This is why malignant is the best fit here—it conveys both the cancerous nature and the tendency to spread, which makes it serious.

The other options don’t fit because they describe different concepts: not harmful in effect describes a benign condition, a rapid heartbeat is tachycardia, and an infectious disease refers to an infection. Malignant specifically points to cancerous, spreading disease.