C#.NET String.Insert: determine the output of String s1 = 'Nagpur'; String s2; s2 = s1.Insert(6, 'Mumbai'); Console.WriteLine(s2); What is printed?

Introduction / Context:
This checks understanding of the String.Insert method, which returns a new string by inserting a specified substring at a given index (0-based).

Given Data / Assumptions:

• s1 = 'Nagpur' (length 6).
• We call s1.Insert(6, 'Mumbai').
• Index 6 equals the length of s1, so insertion occurs at the end.

Concept / Approach:
The Insert method does not mutate s1 (strings are immutable); it produces a new string with the substring inserted at the specified index: prefix up to index + inserted text + remainder. If the index is equal to the original length, it appends.

Step-by-Step Solution:

Verification / Alternative check:
Replace the index with 0 to see a different effect ('MumbaiNagpur'). Attempting an index > length would throw an ArgumentOutOfRangeException.

Why Other Options Are Wrong:
'NagpuMumbair' misplaces letters. 'Nagpur Mumbai' implies insertion of a space not present in the call. 'Mumbai' or 'Nagpur' would imply ignoring one of the strings; that is not the behavior of Insert.

Common Pitfalls:
Confusing Insert with Concat and off-by-one errors with indexes.

Final Answer:
NagpurMumbai