CCl4 is used as a fire extinguisher because:
a) Its melting point is high
b) It forms covalent bonds
c) Its boiling point is low
d) It gives incombustible vapors

CCl
4
​
(carbon tetrachloride) is used as a fire extinguisher because:

d.) It gives incombustible vapors.

When carbon tetrachloride is released as a vapor, it can displace oxygen in the surrounding environment, making it difficult for a fire to sustain itself. Essentially, it acts as a fire suppressant by removing one of the key elements necessary for combustion: oxygen. This makes it an effective fire extinguisher, particularly for certain types of fires, but it's important to note that the use of carbon tetrachloride has declined due to environmental and health concerns associated with its toxicity. Modern fire extinguishers use safer alternatives.