The file extension .ppt is used for files created by:

File extensions are crucial for identifying the type of file and the application it's associated with. The .ppt extension (and its newer counterpart, .pptx) is universally recognized as the standard file format for presentations created using Microsoft PowerPoint.

• Option C, MS PowerPoint, is correct because it is the application that creates and uses files with the .ppt extension.
• Option A, MS Word, uses .doc or .docx for documents.
• Option B, MS Excel, uses .xls or .xlsx for spreadsheets.
• Option D, MS Access, uses .mdb or .accdb for databases.