The correct answer is option 1. Very dear.
The most appropriate meaning of the idiom "apple of one's eye" is Very dear
"Apple of one's eye" is a term of endearment used to describe someone or something that is cherished or loved above all others. It emphasizes a deep affection and importance.
Very harmful, very useful, and very far all have different meanings and don't relate to the concept of expressing fondness. | 
