Explanation/Reference:
The term "software multitenancy" refers to a software architecture in which a single instance of software runs on a server and serves multiple tenants. A tenant is a group of users who share a common access with specific privileges to the software instance.
Incorrect:
Not A: Availability zones (AZs) are isolated locations within data center regions from which public cloud services originate and operate.
Not B: A fault domain is a set of hardware components - computers, switches, and more - that share a single point of failure.
Not D: Zones of trust are a defined area of the system where by by necessity, by the presence of key information assets and by the wider environmental context the connections within the zone are treated as at the same level of trust. This effectively couples the components within that subsystem for security purposes.
References:
https://en.wikipedia.org/wiki/Multitenancy