根据所学知识填空：

    Li Ping is going to England. He wants to know something about English people. One day he sees an English girl in the street. Then he comes up to her.

    “Excuse me, may I ask you some questions?”

    “Of course you may.” answers the girl politely.

    “I'll go to London. What should I notice when I'm talking with English people in London? ”asks Li Ping.

    “Well, don't ask a woman how old she is and…”

    “But how old are you? ”Li Ping stops the girl and asks suddenly.

    “I…”The girl gets angry.

    “Why do you get so angry?”asks Li Ping. “Now we are in China, not in England, you see”

如图，点O是△ABC内一点，连结OB、OC，并将AB、OB、OC、AC的中点D、E、F、G依次连接，得到四边形DEFG．