如图，已知△ABC中，AC＜BC，分别以点A、点B为圆心，大于$\frac{1}{2}$AB长为半径作弧，两弧交于点D、点E；作直线DE交BC边于点P，连接AP．根据以上作图过程得出下列结论，其中不一定正确的是（　　）

在北方的农村，往往有贮藏蔬菜瓜果的地窖，当人们进入地窖之前往往要先用烛火做实验，如果烛火熄灭，人们就不会进入地窖。烛火在地窖中熄灭，说明地窖中缺少____，此时，地窖中的蔬菜瓜果的呼吸作用比较____（填“强或弱”）。

    I am a student. I like sports. I run every morning and I swim twice a week(一周两次). I like all kinds of ball games. I like football, basketball, volleyball, tennis and ping­pong. I am good at playing ping­pong. I often play ping­pong with my friend, Li Lei. We are on the school team. But he doesn't like any other ball game. He also likes to collect(收集)balls. He has a great collection(收藏品)of balls. He has 60 footballs, 16 volleyballs and many ping­pong balls. We like to watch sports on TV.

鉴别氮气和二氧化碳两种无色无气味的气体的最适宜的方法是（）