Help Dr. Fizzle program his clumsy robot. Choose the correct word to complete the command.

The robot must hold a raw egg gently in ___ hand without breaking them!

The correct answer is each.

We use each (not every) when referring to exactly two things, such as a person's or robot's two hands.

All and both are incorrect here because they would require the plural noun "hands" (e.g., "in both hands").