In Multiple Regression Analysis, the Word "Linear" in the Term

In multiple regression analysis, the word "linear" in the term "general linear model" refers to the fact that_____.

A) β₀, β₁, . . . β_p, all have exponents of 0
B) β₀, β₁, . . . β_p, all have exponents of 1
C) β₀, β₁, . . . β_p, all have exponents of at least 1
D) β₀, β₁, . . . β_p, all have exponents of less than 1