结构推理 Questions 1 to 5 are based on the following passage. Did you know that our first 5-cent coin was not a nickel and our first "nickel" was not a 5-cent coin? The coin we now call the "nickel" originated (起源) as a silver half dime（角币）in 1792, the beginning of its 79 year life as a silver 5-cent coin. Our first nickel coins were not 5-cent pieces at all. Nickel first appeared in United States coinage（造币）with the introduction of the small size 1-cent pieces in 1856. Its composition was mostly copper (铜) and less than 1/6 nickel. The nickel caused the coin to be much lighter in color than the older copper coins. For that reason, it was sometimes called a white cent. Another common name was a "nick" --- short for nickel --- referring to its nickel content. This composition was continued in the cent into 1864. The first "nickel" 5-cent piece to be struck was the Shield Type starting in 1866. The composition of the coin was three-quarters copper and one quarter nickel, the same as today's nickels. That means the metal that gives the coin its name is only 25/% of its content! The Shield type was replaced by the Liberty Head or "V" Nickel in 1883 and the Indian Head, more commonly called the "Buffalo" Nickel in 1913. Our current "Nickel," was introduced in 1938, the result of a public competition among some 390 artists. (236 words) 1. What was the first American 5-cent coin made of? 2. When did nickel appear in the United States? 3. Why was the nickel called "white cent"? 4. How much nickel did the first "nickel" have? 5. How was the current "Nickel" was introduced?