How do you reference a positional parameter after $9?

• A. $10, $11, etc.
• B. ${10}, ${11}, etc.
• C. ${9+1}
• D. $9+1

Answer: (B)

Referencing positional parameters beyond the ninth requires braces to clearly mark the parameter name. Once you reach two-digit indices, the shell needs ${10}, ${11}, and so on, rather than $10, to avoid ambiguity about where the parameter name ends. The brace form not only identifies the exact parameter, it also lets you safely attach extra characters or text, for example ${10}suffix or ${10}-more. This makes the expansion robust across shells and contexts. The other forms either don’t refer to the intended parameter correctly (arithmetic-like ${9+1} isn’t how you pull a positional parameter) or break when you try to append text, so they’re not reliable.