下列说法正确的是（   ）

①经分析某物质只含有一种元素，则该物质一定是单质；

②质子数相同，电子数也相同的粒子，不可能是一种分子和一种离子；

③碱性氧化物一定是金属氧化物；

④NO₂不是酸性氧化物、Na₂O₂不属于碱性氧化物；

⑤两种盐反应一定生成两种新盐．

已知 $\left\{a_n\right\}$ 是等差数列，其前 $n$ 项和为 $S_n$ ， $\left\{b_n\right\}$ 是等比数列，且 $a_1=b_1=2$ ， $a_3+b_3=16$ ， $S_5=8+b_5$ .

        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 online. It’s great fun to play 3D games. But playing 3D games for long is not good for our study.

《人民日报》载文指出，个别地方领导干部急功近利、心浮气躁，不太愿意做见效慢、但能让群众长期得实惠的工作，而是盲目追求高速度和轰动效应，热衷于短期行为和华而不实的“面子工程”、“形象工程”。其实，此类政绩越多，人民群众受害愈深，国家利益受损愈重。这些现象说明：
①政府及其公职人员的工作应依靠人民的支持
②政府及其公职人员不能把为人民服务停留在口头上，要落实在实际行动中
③政府及其公职人员的工作应经得起实践、群众和历史的检验
④政府及其公职人员应为公民求助提供多种途径

”小鼠学走迷宫获得食物”和”失去雏鸟的红雀喂养金鱼”从行为获得的方式看分别属于(   )