C#.NET — Which is the correct way to find the index of the second 's' in the string: "She sells sea shells on the sea-shore"? Choose the valid code snippet that correctly identifies the second occurrence.

Introduction / Context:
Locating the second occurrence of a character in a string is a standard string manipulation problem. In C#.NET, the IndexOf method is heavily used to search for substrings or characters, and it has an overload that accepts a starting index. This makes it possible to find subsequent occurrences of a character.

Given Data / Assumptions:

• We are working with the string "She sells sea shells on the sea-shore".
• We want the index of the second lowercase 's'.
• The operation must be case-sensitive; uppercase S at the beginning is not the same as lowercase 's'.

Concept / Approach:
The proper approach is to find the first occurrence using IndexOf("s"). Then, to locate the second occurrence, use the overload IndexOf("s", i + 1), which searches the string starting from the next index position after the first match.

Step-by-Step Solution:

Verification / Alternative check:
A manual scan of the string shows lowercase s at positions 6 (in "sells") and 10 (in "sea"). The code correctly returns index 10 for the second occurrence.

Why Other Options Are Wrong:
(a) SecondIndexOf does not exist in .NET. (b) FirstIndexOf is not a valid method. (d) LastIndexOf finds the last occurrence, not the second. (e) Mixing uppercase and lowercase S incorrectly addresses the wrong character.

Common Pitfalls:
Forgetting that strings are zero-indexed or confusing uppercase and lowercase letters. Another frequent mistake is not incrementing the start index, which would simply return the same first occurrence again.

Final Answer:
String str = "She sells sea shells on the sea-shore"; int i, j; i = str.IndexOf("s"); j = str.IndexOf("s", i + 1);