Question: What is the cause of 'Cannot modify header information - headers already sent'?

1. You are trying to modify a private value
2. Semicolon missing
3. Using a key on an array that does not exists
4. Some html is being sent before a `header()` command that you are using for a redirect

Answer: The correct answer of the above question is Option D:Some html is being sent before a `header()` command that you are using for a redirect