Which character string identifies a file as a shell script?

A shell script is typically identified by a line at the start of the file called a shebang, which specifies the interpreter that should be used to execute the script. The correct option, which includes the shebang #!/bin/sh, indicates that the script should be run with the Bourne shell (sh) interpreter. This is a common convention for shell scripts in Unix-like operating systems.

While other options also contain valid shebangs, they specify different interpreters: one for Python and one that uses the environment to find the interpreter, as well as another indicating the Bash shell specifically. However, since the question specifically asks which character string identifies a shell script in a general sense, the most appropriate answer is the one that explicitly references the Bourne shell, which is at the core of many shell scripting capabilities. This highlights the foundational nature of sh in shell scripting.