如图所示，阻值为R的电阻丝，用四种方法分别接在电压为U或2U的电源上．闭合开关后，在相同时间内虚线框里的电阻丝产生的总热量最多的是（　　）

将矩形ABCD沿AE折叠，得到如图所示的图形，已知∠CED′=55°，则∠BAD′的大小是（   ）

一批零件600个，一个工人每小时做15个，用关系式表示人数x与完成任务所需的时间y之间的函数关系式为　____ 　．

阅读《曹刿论战》回答问题。
      十年春，齐师伐我。公将战。曹刿请见。其乡人曰：“肉食者谋之，又何间焉？”刿曰：“肉食者鄙，未能远谋。”乃入见。问：“何以战？”公曰：“衣食所安，弗敢专也，必以分人。”对曰：“小惠未徧，民弗从也。”公曰：“牺牲玉帛，弗敢加也，必以信。”对曰：“小信未孚，神弗福也。”公曰：“小大之狱，虽不能察，必以情。”对曰：“忠之属也。可以一战。战则请从。”
      公与之乘。战于长勺。公将鼓之。刿曰：“未可。”齐人三鼓。刿曰：“可矣。”齐师败绩。公将驰之。刿曰：“未可。”下视其辙，登轼而望之，曰：“可矣。”遂逐齐师。
      既克，公问其故。对曰：“夫战，勇气也。一鼓作气，再而衰，三而竭。彼竭我盈，故克之。夫大国，难测也，惧有伏焉。吾视其辙乱，望其旗靡，故逐之。”

阅读下列短文，从每题所给的四个选项（A、B、C和D）中，选出最佳选项。

    There are many useful suggestions that can help one to improve English. Here are some of them to increase one's English language vocabulary.

    Learning English vocabulary is about much more than just learning the right words. It is based on understanding important words and expressions.

    Learning a word will not help very much if you quickly forget it. Researches show that it takes from 10 to 20 repetitions(重复) to really make a word part of your vocabulary. Since most words are learned from how they are used in context (上下文), the more words one is shown, the better vocabulary one will have. Keep a piece of paper close to you. When you read, pay close attention to the word you do not know, write the word down and try to understand its meaning from the context. Then look up the word in a dictionary. 

    Remember that if you do not use English words that you have just learned in conversation or writing, you will forget them very quickly. So the best way to learn new words effectively is just by trying to use them in conversation and writing. Remember also that practice is the key to fluent spoken English.

    Building vocabulary is a life-long task. Remember: ＂In the beginning was the word.＂ Your future could depend on how rich your vocabulary is. It will also determine the quality of your communication.