Every April, there is a special day when people remember and honor their ancestors (祖先). It is called Tomb (坟墓)-Sweeping Day, also known as Qingming Festival. This year, the day 1 on April 4th.

    Tomb-Sweeping Day is a(n)2 Chinese festival. It began over 2,000 years ago. A well-known poem by the Tang Dynasty poet Du Mu 3 the day: “Rains fall heavily as Qingming comes, and passersby with lowered spirits go. A drizzling rain falls on the mourning Day, the mourner's heart is breaking on his way.”

    Tomb-Sweeping Day has been a public 4 on the Chinese mainland since 2008. On this day,5 bring flowers, food and wine to their ancestors' tombs (坟墓). They put food like cakes and fruits in front of the tombs. After that, they 6 the dirt (尘土) off the tombs and remember their dead family members.

    7 do Chinese people do this? That's because people think that visiting tombs during Qingming Festival is to 8 respect (尊重) to their dead family members.

    However, Tomb-Sweeping Day is not only about this. During that time, the weather is getting 9. So Tomb-Sweeping Day also means finally being able to garden and enjoy outdoor activities in China. Families often 10 for outings or fly kites at this time.

阅读材料，回答问题。

材料：

    1500—1800年的确是一个空前跨文化交流的时代，它越来越多地影响世界各民族的生活方式和社会组织。早期近代几乎把世界各个民族都纳入彼此经常的、紧密的、持续的联系之中，跨文化交流延伸到东半球、西半球和大洋洲之外，包括了全世界。

    1500—1800年，经过新航路的开辟，无论奢侈品还是大宗商品的运输成本和风险都大大降低了，这些航路上的需求和供给信息可以传播给更广泛地区的商人。各地复杂的货币制度，通过可以互相兑换的黄金、白银、铜币、汇票，也促进了全球贸易。

——摘编自施诚《全球史中的“早期近代”》

解读材料，提炼出一个观点，并结合世界史的其他相关史实，加以论述。（要求：写出观点，观点合理、明确，史论结合。）

把正方形$ABCD$沿对角线$AC$折起,当以$A,B,C,D$四点为顶点的三棱锥体积最大时，直线$BD$和平面$ABC$所成的角的大小为（   ）

沿一个正方体三个面的对角线截得几何体如图所示，则该几何体的侧视图为（　　）