Answer:
B. Hydrogen cyanide
Explanation:
Hello,
In this case, hydrogen cyanide whose formula is HCN and also called prussic acid, is a colorless, venomous and flammable liquid that boils near to room temperature. Now, since it is lighter than air, it rapidly disperses up into the atmosphere, capacity that allows it to poison people as done during the world war two by interfering the body's capacity to transfer oxygen to the cells due to its lightness.
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