下图为岩石圈物质循环示意图，图中①～④四个箭头表示地质作用。岩石圈是指（     ）

下面句中加横线词语运用不正确的一项是（    ）

阅读下面的文言文，完成后面问题。
                                                                                                    荀巨伯探友
        荀巨伯^①远看友人疾，值胡贼^②攻郡，友人语巨伯曰：“吾今死矣，子可去！”巨伯曰：“远来相视，子令吾去。败义以求生，岂荀巨伯所行邪？”贼既至，谓巨伯曰：“大军至，一郡尽空，汝何男子，而敢独止？“巨伯曰：“友人有疾，不忍委之，宁以我身代友人命。”贼相谓曰：“我辈无义之人，而入有义之国。”遂班军^③而还，一郡并获全。
                                                                                                                                                                                                          （选自刘义庆《世说新语·德行》）
【注释】①荀巨伯：东汉颍川（今河南）人。②胡贼：古代泛指西北少数民族的入侵者。 ③班军：撤回军队。

什么叫锐角三角形？并画一个锐角三角形．

阅读下面短文，从短文后各题所给的四个选项（A、B、C和D）中，选出可以填入空白处的最佳选项。

    Wi-Fi is a wireless networking technology used across the globe. A 1 misunderstanding is that the term Wi-Fi is short for “wireless fidelity(保真度)”. However, this is not the case. Wi-Fi is 2 a trademarked phrase that uses the 802.11 standard, which was 3 by the Institute of Electrical and Electronics Engineers (IEEE). That is to say, instead of using 4, your computer is connected to the internet or other computers by radio.

    This standard was 5 promoted by the Wi-Fi Alliance, a trade group that pioneered commercialization of the 6. A person or business can use a wireless router( 路由器) or a similar 7 to create a “hotspot” or an area in which proper devices can connect wirelessly to a network or 8 Internet access. This router is usually connected to the Internet by 9 of a modem, often one   10 as a high-speed connection. Any user within about 200 feet of the 11 point can then connect to the Internet, 12 for good transfer rates, distances of 100 feet or less are often suggested. Salespersons also sell signal boosters（放大器）that  13 the range of a wireless network.

    Wi-Fi networks can either be 14 or closed, in which case a 15 is needed. An area blanketed in wireless access through a device is often called a “wireless 16.” Anyone with a device that  17 proper functionality can connect to this network while in the hotspot. Through this connection, a 18 network can be accessed or Internet connectivity can be achieved. This allows people within the hotspot to connect to the Internet via the router and modem, often 19 for employees at a business or as a free 20 at coffee shops and similar locations.