Hazel's sister has just emailed her an attached file with the invitation list for her upcoming party. Which of these tells what type of file it is?

To determine the type of file attached to Hazel's email, you would need to look at the file extension or format. Common file types for invitation lists might include:

- **.txt** - a plain text file
- **.csv** - a comma-separated values file, often used for spreadsheets
- **.xls or .xlsx** - Microsoft Excel spreadsheet files
- **.doc or .docx** - Microsoft Word document files
- **.pdf** - a portable document format file, which can preserve formatting

Checking the file name at the end or the type of file described (like whether it's a spreadsheet, document, etc.) will provide information on the type of file it is.