'Femto' means ten raised to the power of _____.

-15

The correct answer is option 2. -15.

'Femto' means ten raised to the power of -15.

In the International System of Units (SI), "femto" is a prefix used to denote a factor of \(10^{-15}\). Therefore, when you see a unit prefixed with "femto," it signifies that the quantity is multiplied by \(10^{-15}\).