《中国古代经济简史》指出：康乾年间流通的外国银元除西班牙银元外，还有葡萄牙银元、威尼斯银元、荷兰银元、法国银元等。该现象主要说明（    ）

阅读理解

    A year has twelve months. My favorite month is October. October 1^st is National Day(国庆节）. We have a seven-day holiday(假期). During the holiday, my parents always take me to see my grandparents.

    Our school has some interesting things in October. On the 12th , we have a soccer game. I don't love basket ball. It's difficult for me. But I love soccer. I love playing soccer and watching soccer games. We have a book sale on October 20th. I have three old books and I want to sell them. The art festival is fun. We have it on October 29th. My birthday is also on this day. October is a really great month for me.

有人出于恶作剧或为提高个人网上空间点击率等目的，编造“2010年8月13日　江西抚州将发生6.5级地震”等谣言，并在互联网相关贴吧里发帖，造成了不良影响，触犯了有关法律。公安机关对相关造谣人员分别处以治安处罚。这表明
①公民在网络虚拟世界的行为是不自由 
②公民有使用网络的权利，也有维护网络安全的义务　　
③公民是现实社会的权利主体，但不是网络世界的权利主体
④公民的自由总是在法律规范内的自由

I can _______ well. I want to be a _______.

夏天下暴雨前往往电闪雷鸣，如果在看到闪电4s后听到雷声，求打雷处距人多远？（声音在空气中的传播速度是340m/s，光的传播速度是3×10⁸m/s）