Utterance is based on （）;it is the realization of the abstract meaning of a sentence in a real situation of communication,or simply in a context.

（）is a computer technology that headsets,sometimes in combination with physical spaces or multi-projected environments,to generate realisitic images,sounds and other sensations that simulate a user’s physical presence in a virtual or imaginary environment.

A是三阶矩阵，A，A+E，E-2A均不可逆，则矩阵A的三个特征值是（）。

A single fitting installed in a pipeline that either blanks off the pipe or allows a full flow passage of a liquid through the pipe is referred to as a（）.

What must the Master or person in charge of a ship enter in the logbook after conducting a boat drill? （）

The purpose of the skirt or trunk in four-stroke cycle engines is to act in a similar manner to a （）.

EXCEPT when suffering from a head or chest injury a patient in shock should be placed in which position?（）.

What are symptom(s) of a ruptured appendix?（）

 ______ twice a year, whether it is a car or a bus or a truck, is the rule that every driver must obey in this city.

In the case of an injury causing a person to be incapacitated，the Master or person in charge of a mobile offshore drilling unit must submit a report to the（）.

A lower thermostatic temperature setting will provide a desired degree of comfort in a room where （）

文法G=({E}，{+，*，(，)，a}，P，E)，其中P由下列产生式组成E-＞E+E|E*E|(E)|a。它生成由a，+，*，(，)组成的算术表达式，该文法在乔姆斯基分层中属于(33)型文法，其对应的自动机是(34)，如产生句子a*a+a，它的派生树是(35)，且最左派生由(36)种，该文法是(37)。