The meaning of cross my fingers

THE ANSWER IS (A)

圖片參考：http://ohforfun.typepad.com/oh_for_fun/images/fingerscrossed.gif
這個短語代表的就是“好運，上帝保佑你”的意思。在講這句話時，人們通常會做這樣一個動作：把同一手的中指疊在食指上，兩指交叉（crossed）成X狀
An old superstition says that if you cross your fingers (usually two fingers of the same hand) it will bring good luck.
Cross my fingers refers to actually crossing your fingers, usually the middle finger over the index finger.

Crossing your fingers can have several meanings depending on context, most dealing with superstitions or children's games.

You can cross your fingers to bring good luck. I'll keep my fingers crossed so everything will turn out okay

You can cross your fingers when saying something so that it "doesn't count." I said it, but I had my fingers crossed behind my back so it doesn't count."

www.phrases.org.uk/bulletin_board/44/messages/768.html

If you say that you are crossing your fingers about something, you mean that you are hoping that everything will happen as you want it to. Sometimes you don't have to say anything at all, but simply put your middle finger on top of your forefinger to indicate your hope.

The answer to your question is therefore (a).