The correct answer is: B. It breaks the electron transport chain.
Cyanide is a very toxic substance that can cause death in seconds. It works by inhibiting the electron transport chain, which is a series of proteins that are responsible for producing ATP, the energy currency of the cell. When the electron transport chain is inhibited, cells are unable to produce ATP and they quickly die.
Option A is incorrect because cyanide does not denature enzymes of the heart/muscle. Cyanide does not specifically target any one type of cell or organ. It inhibits the electron transport chain in all cells, which leads to cell death.
Option C is incorrect because cyanide does not cause lysis of red blood cells. Lysis of red blood cells is a condition in which the red blood cells rupture, releasing their contents into the bloodstream. This can be caused by a number of things, including infection, certain medications, and autoimmune diseases. Cyanide poisoning does not cause lysis of red blood cells.
Option D is incorrect because cyanide does not cause cardiac arrest. Cardiac arrest is a condition in which the heart stops beating. This can be caused by a number of things, including a heart attack, a stroke, and an arrhythmia. Cyanide poisoning can cause cardiac arrest, but it is not the only cause.
In conclusion, the correct answer is: B. It breaks the electron transport chain.