Which of the Following Is an Assumption on Which Time

Multiple Choice

Which of the following is an assumption on which time series regression is based?

A) A time series process follows a model that is nonlinear in parameters.
B) In a time series process, no independent variable is a perfect linear combination of the others.
C) In a time series process, at least one independent variable is a constant.
D) For each time period, the expected value of the error u_t, given the explanatory variables for all time periods, is positive.