Which of the Following Is One Way to Detect Autocorrelation

Multiple Choice

Which of the following is one way to detect autocorrelation?

A) Estimate a standard OLS model and look at sign of coefficient.
B) Graph the residuals over time.
C) Estimate an auxiliary regression where the value of X is the dependent variable and the lagged value of X is the independent variable.
D) Estimate an auxiliary regression where the value of e (the residual) is the dependent variable and the lagged value of X is the independent variable.