5. You have time series data for OECD countries. You want to obtain summary statistics for variables X, Y and Z for the year 2021 and the UK. Which of the following STATA command is correct? (A) summarize X Y Z if year==2021 & country==UK (B) summarize X Y Z if year=="2021" & country=="UK" (C) summarize X Y Z if year==2021 & country=="UK" (D) summarize X Y Z if year=2021 & country=UK (E) None of the above