Many English words describing fears are built from a Greek or Latin root that names the object of the fear, followed by "phobia". In "pyrophobia", the root "pyro" is the same root found in words like pyrotechnics, meaning fireworks, and pyromaniac, meaning someone with an urge to set fires. In every one of these words, pyro consistently points to fire.
Following that pattern, pyrophobia has to mean an intense fear of fire, which is exactly what option 4 states, confirming it as the correct answer.
The other options rely on the word sounding like something else rather than its actual root. "Fear of pythons" mixes up pyrophobia with the fear of snakes, a different phobia entirely with a different root. "Fear of funeral pyres" picks up on the fact that pyres are lit with fire, but this narrows the definition down too much, since pyrophobia covers fire in any form, not just pyres. "Fear of fever" borrows from the medical term pyrexia, which relates to body temperature, not to pyrophobia. Because the defining root pyro always means fire across related English words, the correct and complete meaning of pyrophobia is fear of fire, matching option 4.