柱塞偶件由柱塞和柱塞套组成，是（）的核心组件。这个精密偶件，_爱下问搜题

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问题单项选择题

柱塞偶件由柱塞和柱塞套组成，是（）的核心组件。这个精密偶件，成对加工研配，成对使用和更换。

A、喷油泵

B、喷油器

C、机油泵

D、燃油泵

答案

参考答案：A

单项选择题

（）是以预期收益和标准差为坐标轴的画面上，表示风险资产的最优组合与一种无风险资产再组合的组合线。

A.证券市场线

B.无差异曲线

C.资本市场线

D.有效边界

填空题

Column A: the main features of the Direct Method

①The students are encouraged to learn to think in the target language.
②The target language is used exclusively in the language classroom.
③Grammar is learned inductively.
④Oral communication skills are regarded as basic.
⑤The basic unit in a language is the sentence.

Column B: the advantage or disadvantage associated with the feature

a. Regarding listening and speaking as the basis of reading and writing is strategic in fostering the four skills.
b. Thinking in the target language is necessary in efficient real communication.
c. Learners lack a necessary knowledge of the target language grammar.
d. It is difficult to teach the meaning of abstract concepts.
e. Using full sentences as teaching units makes foreign language learning more natural and efficient.