'fetchrow_hashref()' returns a reference to the hash of row values keyed by what?

Answer: Option B

This question is about the `fetchrow_hashref()` function in MySQL. This function is used to retrieve data from a database and store it in a special data structure called a hash.

Imagine a hash as a container where you store information. Each piece of information has a unique label (like a name tag) that helps you find it quickly. In the case of `fetchrow_hashref()`, the labels are the column names of the table you are querying.

So, when you use `fetchrow_hashref()`, the function will return a hash where each row's data is stored. You can access this data using the corresponding column names as keys.

Therefore, the correct answer is Option B: column name.