文献收集可分为如下步骤：（）。

根据研究者对访谈结构的控制程度，可分为（）。

A．直接访谈
B．间接访谈
C．结构访谈
D．半结构访谈
E．非结构访谈

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In the following essay, each blank has four choices. Choose the best answer and write down on the answer sheet. Microwave communication uses(66)-frequency radio waves that travel in straightline sthrough the air. Because the waves cannot(67)with the curvature of the earth, they can be(68)only over short distance. Thus, microwave is a good(69)for sending data between buildings in a city or on a large college campus. For longer distances, the waves must be relayed by means of' dishes' or(70). These can be installed on towers, highbuildings, and mountain tops.A．highB．lowC．longD．short

A.
B.
A．high
B．low
C．long
D．short

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