Question: What is the default case sensitivity of the JSON `Unmarshal` function?

1. The default behavior is case insensitive, but it can be overridden.
2. Fields are matched case sensitive.
3. Fields are matched case insensitive.
4. The default behavior is case sensitive, but it can be overridden.

Answer: The correct answer of the above question is Option A:The default behavior is case insensitive, but it can be overridden.