在△ABC中，∠A=120°，AB=4，AC=2，则sinB的值是（　　）

先通读下面的短文，掌握其大意，然后在每小题所给的A、B、C、D四个选项中，选出可以填入空白处的最佳选项。
    Some young people are worrying about acnes(青春痘) on their faces, and some are worrying about their figures(身材). Do you know 1 on earth（到底，究竟） the secret of beauty is? Think of smile and health, and then you may find the 2 .
    Maybe you are not 3 with your big nose, your small 4 or your weight(体重). Don't waste energy and feelings on the way you look . In fact, when you become an 5 and look at pictures of your past time, you'll find how cute you are.
    6 is the best way to make you beautiful. When people are happy, they look nice. When people smile or laugh from the7 of their hearts(心脏), they look very beautiful.
    Don't worry about your weight too much. Don't 8 food for it. No one lives 9 health. So you need to eat healthy food and do enough exercise.
    When you accept（接受） what you have 10 and enjoy them, you will really become pretty “inside and out”.

反应A（g）+B（g）⇌C（g）+D（g）过程中的能量变化如图所示，下列说法正确的是（   ）

利用如图装置探究平面镜成像特点

（1）实验时应选 ____（较厚/较薄）的玻璃板代替平面镜竖立在水平桌面上．

（2）在玻璃板前放置棋子A，将完全相同的棋子B放在玻璃板后并移动，人眼一直在玻璃板的前侧观察，直至B与A的像完全重合，由此可得结论： ____．

（3）为了探究平面镜成像的虚实情况，将一张白卡片竖直放在B所在的位置，应在玻璃板 ____（前/后）侧观察白卡片上是否有A的像．

（4）改变A的位置，重复（2）中步骤并分别测出A和B到玻璃板的距离，记录在下表中．

序号	1	2	3
A到玻璃板的距离/cm	3.00	5.00	8.00
B到玻璃板的距离/cm	3.00	5.00	8.00

分析表中数据，可以得到结论 ____

如图所示，是“探究影响压力作用效果的因素”实验。