In Bash scripting, what symbol is required at the beginning of the script?

The symbol required at the beginning of a Bash script is known as a shebang, represented by the sequence #!/bin/bash. This line tells the operating system which interpreter to use to execute the script. Specifically, the #! indicates that what follows is the path to the interpreter, which in this case is /bin/bash.

By placing this shebang at the top of the script file, you ensure that when the script is run, it will be executed using the Bash shell regardless of the current shell that the user might be using. This is critical for ensuring that Bash-specific syntax and features are properly interpreted.

The other options fail to specify the correct syntax for the shebang. In particular, #!bin/bash is missing the leading slash before bin, making it an invalid path. The entries bash! and bin/bash! lack the proper shebang structure entirely, as they do not include the # symbol and are formatted incorrectly for specifying an interpreter.