You can sort by multiple columns using the sort command by doing what argument?

• A. Use a single -k with a primary key.
• B. Use three -k arguments for multi-level sorting.
• C. You need two -k arguments. They're sorted first by the first -k argument and then if any of those match, then it's sorted by the second -k argument.
• D. Use -K to specify a temporary file.

Answer: (C)

Sorting by multiple columns is done by providing multiple key specifications with the sort command. The first key acts as the primary sorting criterion; if two lines share the same value for that key, the next key is used to break the tie, and so on. That’s why this approach uses two -k options: the first defines the primary column to sort by, and the second defines the secondary column to use when there are equal values on the first. If you only specify one -k, you sort by that field and ties aren’t further distinguished by another key unless you add another -k. For example, sort -k 1,1 -k 2,2 file will sort primarily by the first column, and within equal first-column values, it will sort by the second column.