Human language is a living thing. Each language has its own biological system, which makes it different from all other languages. This system must constantly adjust to a new environment and new situations to survive and flourish (兴盛).When we think of human language this way, it is an easy step to see the words of a language as being like the ceils of a living organism (机物)-they are constantly forming and dying and splitting into parts as time changes and the language adapts.There are several specific processes by which new words are formed. Some words come into the language which sound like what they refer to. Words like buzz (嗡嗡) and ding-dong are good examples of this process.Still another way in which new words are formed is to use the name of a person or a place closely associated with that word’s meaning. The words sandwich and hamburger are examples of this word-formation process. The Earl ( 伯爵 ) of Sandwich was so fond of gambling at cards that he hated to be interrupted by the necessity of eating. He thus invented a new way of eating while he continued his game at the gambling table. This quick and convenient dish is what we now call a sandwich-a piece of meat between two slices of bread. The hamburger became the best-known sandwich in the world after it was invented by a citizen of Hamburg in Germany.As long as a language is alive, its cells will continue to change, forming new words and getting rid of the ones that no longer have any use. How many ways of word-formation are mentioned in the article（）

A. Two.
B. Three.
C. Four.
D. Five.