Rita's smartphone uses an open source operating system. Which of the following…

Concept

"Open source" is a statement about the licence under which software is distributed: the licence releases the human-readable source code to the people who receive the program and grants them the right to study it, modify it and pass it on.

Distribution of the code is a separate attribute from copyright ownership, from how safe a system turns out to be in practice, and from how much processor time it consumes. Each of those is fixed by different factors — the licence terms and the copyright holder, the review and patching regime, and the design and build of the software respectively — so none of them follows automatically from the licence type.

Applying it to this question

Rita's phone runs an open source operating system, so by definition that operating system's source code is published under a licence that puts the code itself in the hands of its users, who may read it, change it and redistribute it. The statement that describes the source code is therefore that it is made available to users.

Contrasting the other statements

• "It is owned by the company who developed it." — describes copyright. Open source code still has a copyright holder; what the open source licence changes is what the holder permits others to do with the code, not that ownership disappears.

• "It is more secure." — describes an outcome of running the system. Public code can be audited by more people, but the security a user actually gets depends on how quickly defects are found, patched and installed, so it is not a description of the source code.

• "It uses less processing power." — describes runtime resource consumption, which follows from kernel design, the feature set that is compiled in and the build configuration, not from the terms of the licence.

Cross-check

A useful test: change only the licence of a program and leave every line of code untouched. Its copyright holder, its measured CPU usage and its defect count are all unchanged; the one thing that changes is whether users receive the source code. That isolates availability of the code as the property the term "open source" names.