Question: Which line of code shows how to display a nullable string's length and shows 0 instead of null?

1. `println(b!!.length ?: 0)`
2. `println(b?.length ?: 0)`
3. `println(b?.length ?? 0)`
4. `println(b == null? 0: b.length)`

Answer: The correct answer of the above question is Option B:`println(b?.length ?: 0)`