The correct answer is A. OEM. A vendor/manufacturer website is an original equipment manufacturer source when it is owned by the company that made or provides the software or driver. The question says the driver is found on the vendor's website, not an app store, third-party site, or SaaS platform. SaaS means Software as a Service and refers to cloud-hosted applications, not a printer driver download source.
Exact Extract/Reference: The Tech+ Study Guide states that "An original equipment manufacturer (OEM) website is one owned by the developer of the software," and that software from an OEM website is legitimate and trusted. It also gives a printer driver example where the HP support site is identified as an OEM website.