A(n) ________ is a stream of historical data.

A) index
B) time series
C) irrational number
D) orthopole

A time series is a stream of historical data, usually collected at regular intervals. Index refers to a list of data points or values, irrational numbers are real numbers that cannot be expressed as a ratio of integers, and orthopole is a term used in mathematics and physics to describe a point that is perpendicular to several lines or planes. None of these definitions match the description of a stream of historical data.