Game on! 1 simple question! Win 0.5 sbd

Wild guess!
But first the rules!

1. Upvote this post
2. Comment the answers below
3. Invite people to guess ( one guess per person )
4. Challenge your friends

There are four girls above, only two of them are blood sisters. Choose the right answer and win 0.5 sbd.

Contest ends at 16th May 8:00pm.

Note: Result to be announced 7days later along with the winners