【正确答案】The particular dialect or language that a person chooses to use on any occasion is a code, a system used for communication between two or more parties. "Code switching" basically means switching back and forth between two or more languages in the course of a conversation. It can also refer to the ability to switch languages or dialects quickly from one conversation to the next depending on the situation or conversation partner. For example, a child who has an English- speaking mother and a Japanese-speaking father may speak only English with the mother and only Japanese with the father even though they all speak both languages and are all participating in the same conversation. There are two kinds of code-switching: situational and metaphorical. Situational code-switching occurs when the languages used change according to the situations in which the conversants find themselves: they speak one language in one situation and another in a different one. No topic change is involved. When a change of topic requires a change in the language used we have metaphorical code-switching.
It is unusual for a speaker to have command of, or use, only on such code or system. Command of only a single variety of langue, whether it be a dialect, style, or register, would appear to be an extremely rare phenomenon, one likely to occasion comment. Most speakers command several varieties of any language they speak, and bilingualism, even multilingualism, is the norm for many people through the world rather than unilingualism. People, then, are usually required to select a particular code whenever they choose to speak, and they may also decide to switch from one code to another or to mix codes even within sometimes very short utterances and thereby create a new code. Furthermore, code-switching is a conversational strategy used to establish, cross or destroy group boundaries; to create, evoke or change interpersonal relations with their rights and obligations.
The actual choice of code in a setting clearly marked as bilingual can be a difficult task. Language plays a symbolic role in our lives, and when there is a choice'of languages the actual choice may be very important, particularly when there is a concurrent shift in the relationship between the languages, as is occurring in Montreal between English and French.
In a multilingual country like Singapore, the ability to shift from one language to another is accepted as quite normal. Singapore has four official languages: English, the Mandarin variety of Chinese, Tamil, and Malay, which is also the national language.
Tanner (1967) reports on the linguistic usage of a small group of Indonesian graduate students and their families living in the United States. Among them these students knew nine different languages, with nearly everyone knowing Indonesian, Javanese, Dutch, and English. They tended to discuss their academic work in English but used Indonesian for most other common activities.
In Kenya local languages, Swahili, and English all find use and choosing the right language to use on a particular occasion can be quite a delicate matter.

【答案解析】[解析] 本题主要考查语码转换(code-switching)的定义和理解。答题时要注意先说清什么是语码转换，再进一步说明语码转换的必要性和重要性并举例说明。