Which flag in RSYNC is used to preserve modify times during file transfer?

The flag used in RSYNC to preserve modify times during file transfer is indeed -t. When this flag is included in the RSYNC command, it ensures that the timestamp of the source files is preserved in the destination. This means that the files in the destination will retain their original modification times, which can be crucial for maintaining accurate file versioning and for applications that rely on the timestamp for function.

Preserving modify times is particularly important in backup and synchronization tasks, as it allows users to identify the last updated state of files accurately.

The other options serve different purposes: -g is used to preserve group ownership of the files, -D is typically used to preserve device files and special attributes, and -j does not pertain to any relevant functionality in RSYNC. Thus, the -t flag is the correct choice for preserving modification times.