Fail-open is a feature that allows traffic to pass through the IPS sensor without inspection when the sensor fails or is overloaded. If fail-open is set to disable, traffic will be dropped in such scenarios1. References:
= IPS | FortiGate / FortiOS 7.2.3 - Fortinet Documentation
When IPS (Intrusion Prevention System) is configured, if fail-open is set to disable, it means that if the IPS engine fails, traffic will not be allowed to pass through, which can result in traffic being dropped (D). This is in contrast to a fail-open setting, which would allow traffic to bypass the IPS engine if it is not operational.

Option D is the correct answer because it specifically blocks access to the website "www.eicar.org" using TCP protocol and HTTP service, which are commonly used for web browsing. The other options either use the wrong protocol (UDP), the wrong service (DNS or SSL), or the wrong pattern ("eicar" instead of "www.eicar.org"). Reference := Configuring custom signatures | FortiGate / FortiOS 7.4.0 - Fortinet Document Library, section "Signature to block access to example.com".

In the Security Fabric, only the root FortiGate sends logs to FortiAnalyzer (B). Additionally, only FortiGate devices withconfiguration-syncenabled receive and synchronize global Central Management Database (CMDB) objects that the root FortiGate sends (C). FortiGate uses the FortiTelemetry protocol to communicate with other FortiGates, not FortiAnalyzer (A). The last option (D) is incorrect as all FortiGates can collect and forward network topology information to FortiAnalyzer.
References:
* FortiOS Handbook - Security Fabric