Other source:
After Goku's shocking declaration, Cell claims victory over Earth. But, Goku says that Cell has one more competitor to fight. Cell has already fought and defeated Vegeta, Trunks, and Piccolo, and these three are supposed to be the strongest of the remaining fighters. Goku stuns everyone by selecting Gohan. He claims that Gohan's strength far exceeds his own. Despite the rest of the Z fighters protests, and even despite the fact that Goku willingly gives Cell one of their senzu beans, Goku remains confident in Gohan's strength. Gohan then powers up and begins his battle with Cell.
