Which of the following commands can help troubleshoot memory usage by processes?

All of the commands listed—ps, top, and htop—are useful tools for troubleshooting memory usage by processes in a Linux environment.

The 'ps' command provides a snapshot of current processes and their resource usage, including memory. It can show details such as the amount of RAM each process is using, which is pivotal for identifying memory hogs and understanding overall memory distribution.

The 'top' command is an interactive utility that gives real-time updates regarding system processes, CPU usage, and memory consumption. It is particularly beneficial for monitoring system performance dynamically and quickly identifying processes that utilize excessive memory resources as they change over time.

The 'htop' command is an enhanced version of 'top' with a more user-friendly interface and additional features. It offers better visibility into process management, allowing users to sort processes by various criteria, including memory usage. The color-coding and graphical elements make it easier to identify problematic processes.

Using all these tools together provides a comprehensive approach to monitoring and troubleshooting memory usage in processes, therefore supporting the idea that they collectively aid in diagnosing memory-related issues.