Question: Assuming that `$first_name` and `$family_name` are valid strings, which statement is invalid?

1. `echo $first_name. ' '. $family_name;`
2. `print $first_name, ' ', $family_name;`
3. `print $first_name. ' '. $family_name;`
4. `echo $first_name, ' ', $family_name;`

Answer: The correct answer of the above question is Option A:`echo $first_name. ' '. $family_name;`