The correct answer is C. Autocorrelation.
Autocorrelation is a statistical measure of the correlation between a variable and its own lagged values. It is a useful tool for checking randomness in time series data. A time series is said to be random if the autocorrelations of its values decay to zero as the lag increases.
Autocausation is a statistical measure of the correlation between a variable and its own future values. It is not a useful tool for checking randomness in time series data.
Autorank is a statistical measure of the rank correlation between a variable and its own lagged values. It is not a useful tool for checking randomness in time series data.
None of the mentioned is not a valid option.