Which of the following is the correct way to find out the index of the second 's' in the string "She sells sea shells on the sea-shore"?

• String str = "She sells sea shells on the sea-shore"; int i; i = str.SecondIndexOf("s");
• String str = "She sells sea shells on the sea-shore"; int i, j; i = str.FirstIndexOf("s"); j = str.IndexOf("s", i + 1);
• String str = "She sells sea shells on the sea-shore"; int i, j; i = str.IndexOf("s"); j = str.IndexOf("s", i + 1);
• String str = "She sells sea shells on the sea-shore"; int i, j; i = str.LastIndexOf("s"); j = str.IndexOf("s", i - 1);
• String str = "She sells sea shells on the sea-shore"; int i, j; i = str.IndexOf("S"); j = str.IndexOf("s", i);