阅读下面短文，按照句子结构的语法性和上下文连贯的要求，在空格处填人一个适当的词或使用括号中词语的正确形式填空，并将答案填写在答题卡标号为3l-40的相应位置上。

Traditional Chinese culture places much emphasis（重视）on food. Considered to be an important part of each day,  __31 __(eat) is far beyond simply meeting a need. However, people are living in fast-paced society now, so they hardly have time to enjoy their food. They need fast food. That is _32_ China’s fast-food market expands.

A foreign fast-food restaurant __33__（call）KFC arrived in China first, quickly followed by _34_ such as Pizza Hut and McDonald’s. __35__ the development of China, foreign fast-food chains are realizing high-speed __36__ (grow) in China. However, these “junk foods” have long been criticized by health experts because __37__ can’t provide balanced nutrition(营养). The experts also show that some foreign fast food contains a food colouring, Sudan I , __38___can cause cancer.

In fact, China has many of its own traditional fast-food dishes. Among them, dumplings, soybean milk and noodles are __39__ most popular. Compared with foreign fast food, those traditional ones are healthier. __40__ many Chinese still enjoy the special taste and the good environment in the foreign fast-food chains even though there exist some potential（潜在的）risks.

从关系模式中指定若干个属性组成新的关系的运算称为______。

A．联接
B．投影
C．选择
D．排序