There have been plenty, but no one's seen them. The question betrays a confusion and lack of understanding on the part of the questioner. None of the above. Love is a feeling. Love is a wanting.
Love is an ideal .
None of the above. Men are always mooning around because of love while women just want sex. There are no differences that make a difference except those systems and cultures construct. Women just know and men try to know. None of the above.