Final answer:
The directory /bin is used to store essential system commands for Unix and Unix-like operating systems. It contains important binaries for booting the system and performing basic operations.
Step-by-step explanation:
The directory used to store commands needed for system operability in Unix and Unix-like operating systems is /bin. Option 1 is the correct answer. The /bin directory contains essential binary executables that are needed to boot the system and to perform basic operations when no other filesystems are mounted. These commands include essential utilities such as ls (to list directory contents), cp (to copy files), and mv (to move or rename files).
Other options mentioned here serve different purposes. For example, /dev contains device files, /etc holds configuration files for the system, and /opt may contain additional software and packages.