Question: How would you write a text string containing "Hello World!" in a way that makes it possible for someone else to translate the string into a different language?

1. `apply_filters( 'Hello World!', 'mytextdomain' );`
2. `esc_html( 'Hello World!', 'mytextdomain' );`
3. `$string = "Hello World!";`
4. `__( 'Hello World!', 'mytextdomain' );`

Answer: The correct answer of the above question is Option D:`__( 'Hello World!', 'mytextdomain' );`