Answers:
A, B, and C.
Explanation:
a. Linux software is unlikely to become abandoned by its developers.
Linux is Open Source, this means that the source code is free and public. Any user or developer can read and contribute by fixing bugs or adding new functionalities, and does not relies on a single group or company.
b. Linux is secure and has a lower total cost of ownership than other operating systems.
Most distributions are totally free to download, install and use for both individual and corporate use, so no licences must be paid. Also the community provides excellent support to questions and issues.
c. Linux is widely available for many platforms and supports many programming languages.
There are multiple distributions designed for practically every platform (personal computers, servers, mobile devices, etc.). Functionalities can can be extended by adding packages, for example, to support different programming languages, like C, Java, Python, and many others, making the system extremely versatile.
d. Most Linux software is closed source.
This one is NOT correct, as is opposite to the "open source" explanation given in a.