Final answer:
The most useful piece of equipment for creating an online property listing is a smartphone, due to its photo and video capabilities, internet access, and compatibility with various apps (C).
Step-by-step explanation:
When creating an online listing of a property for a website or a multiple listing service, the most useful piece of equipment would be a smartphone. This is because a smartphone provides the capabilities to take high-quality photos and videos, access the internet to upload the listing, and use various apps that might be needed for editing pictures or creating the listing content.
In comparison, a printer, tape measure, and ladder have more specific uses that are not directly related to the creation and uploading of an online property listing. Even though a tape measure is useful for obtaining the dimensions of a room, which is important information for a listing, it is the smartphone that will be essential for the overall process of creating and publishing an online property listing.