Which of the Following Statements Correctly Identifies the Difference Between

Which of the following statements correctly identifies the difference between an autoregressive model and a vector autoregressive model?

A) In an autoregressive model, the dependent variable is expressed as a function of its own lag, whereas in a vector autoregressive model, the dependent variable is expressed as a function of the lag of an explanatory variable.
B) In an autoregressive model, the dependent variable is expressed as a function of the lag of an explanatory variable, whereas in a vector autoregressive model, the dependent variable is expressed as a function of its own lag.
C) In an autoregressive model several series are modeled in terms of their own past, whereas in a vector autoregressive model only one series is modeled in terms of its own past.
D) In an autoregressive model one series is modeled in terms of its own past, whereas in a vector autoregressive model several series are modeled in terms of their past.