May 21st this year marks the first International Tea Day, which was named officially 61 the United Nations on November 27th, 2019. To celebrate 62 festival, a number of events took place at the Chinese Businessman Museum in Beijing on Thursday.
The chairman of the China Culture Promotion Society 63 （address）the opening ceremony. "As a main promoter of the International Tea Day, the birthplace of tea and the 64 （large）tea-producing country, China has a 65 （responsible）to work with other countries to promote the healthy development of the tea industry. It can help to build a community with a 66 （share）future for mankind," he said.
The "First International Tea Day Tea Road Cooperative Initiative" issued（发布）at the ceremony calls for people working in the tea industry to come together to promote international cooperation 67 cultural exchanges. A four-year tea promotion—Tea Road Cooperative Plan—was also issued in accordance with the initiative.
68 （strengthen）the connection with young people, the event included a number of public promotional activities on social media, 69 （invite）twenty-nine tea professionals from around the world to have thirty-six hours of uninterrupted live broadcasts.
The Chinese Ancient Tea Museum was officially unveiled（揭幕）at the ceremony, opening 70 （it）first exhibition: The Avenue of Truth—A Special Exhibition of Pu'er Tea.
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用雷达探测一高速飞行器的位置。从某时刻（t=0）开始的一段时间内，该飞行器可视为沿直线运动，每隔1s 5 测量一次其位置，坐标为 x，结果如下表所示：
一种可用于卫星上的带电粒子探测装置，由两个同轴的半圆柱形带电导体极板（半径分别为 R 和 ）和探测器组成，其横截面如图（a）所示，点 O 为圆心。在截面内， R+d极板间各点的电场强度大小与其到 O 点的距离成反比，方向指向 O 点。4 个带正电的同种粒子从极板间通过，到达探测器。不计重力。粒子 1、2 做圆周运动，圆的圆心为 O、半径r1、r2（R＜r1＜r2＜R+d）；粒子 3 从距 O 点r2的位置入射并从距 O 点r1的位置出射，粒子4从距O点r1的位置入射并从距O的r2的位置出射，轨迹如图（b）中虚线所示。则（）
质量为1kg 的物块在水平力 F 的作用下由静止开始在水平地面上做直线运动，F 与时间 t 的关系如图所示．已知物块与地面间的动摩擦因数为 0.2，重力加速度大小取g=10m/s2。则（）
如图，两对等量异号点电荷+q、-q（q＞0）固定于正方形的 4 个项点上。L、N 是该正方形两条对角线与其内切圆的交点，O 为内切圆的圆心，M 为切点。则（ ）
安装适当的软件后，利用智能手机中的磁传感器可以测量磁感应强度 B。如图，在手机上建立直角坐标系，手机显示屏所在平面为 xOy 面。某同学在某地对地磁场进行了四次测量，每次测量时 y 轴指向不同方向而 z 轴正向保持竖直向上。根据表中测量结果可推知（）
