Which one of the following is a valid source name in Google Analytics?

In Google Analytics, valid source names are those that can be used to identify where traffic to a website originates. The option that has been identified as correct, which is (direct), refers to traffic that comes directly to a website without any referrer information. This can occur when a user types the URL directly into the browser or clicks on a bookmarked link.

Sources in Google Analytics help in understanding how users arrive at your site, and the (direct) source plays a crucial role in tracking and analyzing traffic that does not come from identifiable external sources.

The other choices provided represent terms that are not used as source names in Google Analytics. For instance, "utm_source" is a parameter used in URLs for tracking purposes but is not a standalone source name. "campaign_source" might suggest a connection to UTM parameters but does not function as a valid source name itself. Likewise, "websource" is not recognized within the context of Google Analytics for categorizing sources of traffic.