1 zepto is equal to
(A) 10-25
(B) 1025
(C) 10-21
(D) 10-22
(E) None of the above/ More than one of the above
Answer: (C)
A zepto is a unit prefix—like kilo, milli, and centi—in the metric system representing a factor of 10−21, or 0.000000000000000000001.