P: 41 1.Why the object requires prime number p? 2.Why the p-adic norm of x is defined by $$|x|_{p}=p^{-m}$$($$x=\frac{p^{m}r}{s}$$),not $$|x|_{p}=p^{m}$$? 3.$$Q_{p}\subset R$$ or $$R \subset Q_{p}$$? 4.What is the difference between p-adic and l-adic? what is the letter "l" stands for?