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    My swimming experience is extreme interesting. There was a time when I swim like a rock.This went on till one day when I was fishing with a friend of mine at nearby pond. I was so much careless that I slipped into one. Had my friend not come to my rescue, I would have be drowned. Ever since then, I have come to know the importance of learn to swim. I didn't go to any training class but  learned it all by me. Now I have no difficult swimming at all . Though the way I swim looks clumsy ,at least it can keep me floating. Thinking of this, I feel quite satisfying.

—How do you usually come to school, by bus or by bike?

—      . I walk.

在抛物线$y^2=2px\left(p>0\right)$上，横坐标为4的点到焦点的距离为5，则该抛物线的准线方程为(     )

（1）生活中的铝制品和金属制品在常温下都不易腐蚀，请简述其原理．

（2）如何鉴别木炭粉和铁粉．