In SAML 2.0, an Artifact is a reference (a "pointer" or "ticket") used in the SAML Artifact Binding.5 This is an alternative to the more common POST or Redirect bindings where the actual XML assertion is sent through the user's browser.
According to the PingAM "SAML 2.0 Bindings" documentation:
When using the Artifact binding, the Identity Provider (IdP) does not send the full SAML Assertion through the browser.6 Instead, it sends a small, opaque string called the Artifact to the Service Provider (SP).
Issuance: The IdP stores the real assertion in its own local memory/cache and sends the Artifact to the SP via the browser redirect.
Resolution: The Service Provider receives the Artifact and then makes a direct, secureback-channel call(SOAP over HTTPS) to the IdP's Artifact Resolution Endpoint.
Exchange: The SP presents the Artifact, and the IdP returns the actual SAML Assertion.
Therefore, the Artifact is thevalue sent to retrieve the assertion(Option D). It is not the assertion itself (Option A), nor is it a binding name or an attribute name. The Artifact binding is often used for security reasons, as it prevents the sensitive assertion data from ever passing through the user's browser, thus mitigating certain types of interception attacks.
