单选题

　　[阅读选择]People suspected that “Lucky”， as he was called by friends， wanted to kill his wife he no longer lived with. They say that Lucan entered his old house and in the dark， killed the nanny by mistake. His estranged wife heard noises， came downstairs and was also attacked， but managed to escape. Seven months after the murder， a jury concluded that Lucan had killed the nanny.

　　It is thought that Lucan killed the nanny because______.

　　A.she was looking after the children

　　B.she was a friend of Lucan's

　　C.it was dark and he thought she was Lady Lucan

　　D.Loard Lucan thought the nanny stole his car