1 zepto is equal to –

Correct answer: (c) 10⁻²¹

Explanation

The prefix zepto means 10⁻²¹. Its opposite, zetta, means 10²¹.

Other small prefixes: milli 10⁻³, micro 10⁻⁶, nano 10⁻⁹, pico 10⁻¹², femto 10⁻¹⁵, atto 10⁻¹⁸, yocto 10⁻²⁴.