Canadian English is the variety of English spoken in Canada. English, instead of French, is the first language, or “mother tongue”， of approximately 24 million Canadians (77%), and more than 28 million (86%) are fluent in the language.

Canadian English contains elements of British English and American English in its vocabulary, as well as Canadian native language. In many areas, speech is influenced by French, and there are notable local variations. Canada has very little dialect diversity compared to the United States. Canadian English and American English are sometimes classified together as North American English. Canadian English spelling is largely a combination of British and American conventions(惯例)．

The term “Canadian English” is first proved in a speech by the Reverend A. Constable Geikie in a speech to the Canadian Institute in 1857. Geikie, a Scottish-born Canadian, reflected the Anglocentric attitude that would be common in Canada for the next hundred years when he referred to the language as “a ruined dialect，” in comparison to what he considered the proper English spoken by immigrants from Britain.

Canadian English is the product of four waves of immigration and settlement over a period of almost two centuries. The first large wave of long English-speaking settlement in Canada, and linguistically the most important, was the arrival of Loyalists escaping from the American Revolution, chiefly from the Mid-Atlantic states—as such, Canadian English is believed by some scholars to have come from northern American English. Recent studies suggest that Canadian English has been developing features of its own since the early 19th century. The second wave from Britain and Ireland was encouraged to settle in Canada after the War of 1812 by the governors of Canada. Waves of immigration from around the globe peaking in 1910 and 1960 had a lesser influence.

吞咽时，____盖住喉口，以免食物进入____．

某同学做了如图所示的实验：

①向1号、2号试管中各加入2毫升冷却的浆糊；

②再向1号试管中加入2毫升清水，向2号试管中加入2毫升唾液；

③将2支试管充分振荡后，放入盛有温水的烧杯中，10分钟后取出，待冷却后各加入2滴碘液．

请回答：

四年级三个班到工具房领扫把，四年（1）班领走全部扫把的一半少7把，四年（2）班和四年（3）班各领走剩下扫把的一半．最后发现三个班级领的扫把同样多，四年（1）班领了____ 把扫把．