How to select c8 and c18 columns?

To select the C8 and C18 columns from a dataset, you can use data manipulation tools depending on the programming language or software you're using. In Python with pandas, you would use df[['C8', 'C18']], where df is your DataFrame. In R, you would use df[, c("C8", "C18")]. If you're using SQL, you can select these columns from a table using SELECT C8, C18 FROM table_name;.