Who murdered Yassir Arafat?

This requires a "don't know" option too.

Lethal levels of polonium were found in his blood which most people would associate with a hit by Mossad. Or a hit that was supposed to look like it was done by Mossad.

Pollonium is not something easily obtainable.

For one you need to have nuclear infrastructure at your disposal to make it.

As I understand it Polonium is obtained through the decay of uranium ores. Which is a key material used in both nuclear fusion and nuclear weapons. Of which Israel has both.

Though if we look at the poisoning of Alexander Litvinenko who was the first recorded case of Polonium poisoning it would suggest the Russian intelligence agency, FSB or former KGB

Though Occums Razor would suggest the former than the later.