These days, many students like playing 3D games. Do you know what 3D games are like? In most 3D games, game players need to control (控制) a character. The character can be a robot or a soldier (士兵). Game players usually use the mouse to make the character move around in his own world. Game players can find things such as food and weapons (武器) to help them go on with the game. The character can go straight, sit down, turn left, turn right or pick up things in the game.
    Some 3D games have many levels (等级). The character needs to finish different goals for each level.Game players can play against their computers, and sometimes they can play with other players on-line. It's great fun to play 3D games. But playing 3D games for long is not good for our study.

盐城濒临黄海，海盐文化全国知名．某兴趣小组同学去盐场参观，带回了部分粗盐样品，并对其进行了如下探究：

选出正确答语。

① Where is my bag?____                            a. I'm from Canada.

②Is your pencil box on the chair?____       b. OK!

③What's this?____                                  c. It's in your desk.

④Where are you from?____                       d. No, it isn't.

⑤Let's go to school.____                         e. It's a toy bear.

某草地上，生活着蛇和老鼠，下面对这条食物链的分析中，描述正确的是：（　　）

解下列方程：