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问题 单项选择题

使用简易人工呼吸器可一次性挤压进入肺部的气体量是（）

A.100～300ml

B.300～500ml

C.500～700ml

D.500～1000ml

E.1000～1200ml

答案

参考答案：D

单项选择题

Are you interested in seeing the beautiful fall foliage of New England but tired of traffic jams and overbooked hotels Then this year forget the crowds in New England and see the beautiful colors of autumn in the Catskills.
These rugged mountains in New York State, just 90 miles northwest of New York City, are famous for the legendary tales of Rip Van Winkle, and more recently for the summer hotels mat sprang up in the region during the 1940s, 1950s, and 1960s. Families trying to escape the heat of New York City found the Catskills to be the perfect place to stay for a month or so each summer. By the late 1950s there were over 500 resorts and hotels offering nighttime entertainment as well as all kinds of outdoor activities. Famous comedies like Jackie Gleason, Joan Rivers, and Sid Caesar all got their start touring the hotel clubs here. Since the introduction of air-conditioning and cheaper air travel, however, families have stopped coming to the Catskills in such large numbers, chasing instead more distant locations at different times of the year. Many of the Catskills hotels closed in the 1970s, but some remain and have expanded and changed their facilities to meet the needs of today’s visitors.
Currently, there are many activities available to the traveler besides witnessing the changing colors of the leaves. There is an all-organic sheep farm where visitors can see how a traditional sheep farm operates. There are also hundreds of miles of scenic drives in the area. Route 42, for instance, is an excellent site for spotting bald eagles. For more information on vacations in the Catskills, call the office of Public Information.

The author’s main purpose is to ______.

A．promote the Catskills as a vacation destination

B．introduce visitors to famous Catskills entertainers

C．describe the history of the Catskills region

D．compare the Catskills to New England
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单项选择题

三相异步电动机中的磁场为（）。

A．固定磁场

B．脉冲磁场

C．旋转磁场

D．永久磁场
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