In the Unix sort command (historical POSIX/legacy syntax), which position option begins sorting after the nth column of the (m+1)th field?

Introduction / Context:
Older Unix sort utilities (and some current implementations in legacy mode) support field/column specifications using the historical +m.n notation to set the starting key position. Understanding this syntax is valuable when you encounter classic scripts or exam questions referencing it, even though modern sort often prefers the -k option.

Given Data / Assumptions:

• Legacy sort position syntax is being referenced.
• You need to start sorting after the nth column of the (m+1)th field.
• Fields are whitespace-delimited unless specified otherwise.

Concept / Approach:

In the historical format, +m.n indicates the sort key starts at field m+1, column n+1 within that field (semantics vary slightly by implementation, but exam convention treats it as “after nth column of (m+1)th field”). Therefore expressing “(m+1)th field and nth column” is commonly written as +(m+1).n. In the provided options, +(m+l).n uses l to indicate the number one, matching +(m+1).n.

Step-by-Step Solution:

Verification / Alternative check:

Modern equivalent: sort -k $((m+1)).$((n+1)) (adjust for exact column semantics). Recognizing that the question tests legacy notation ensures you select the expression that encodes “after nth column of the (m+1)th field.”

Why Other Options Are Wrong:

• -m.n: wrong flag; minus indicates a different (end) position in some variants.
• +m.n: starts at the m-th field (not m+1 as asked).
• + n.m+1: malformed spacing/syntax.
• None of the above: incorrect because the intended legacy form is present as +(m+l).n.

Common Pitfalls:

• Mistaking legacy +POS for modern -k usage; on GNU sort, prefer -k.
• Off-by-one confusion between field/column indexes in different implementations.

Final Answer:

+(m+l).n.