《史记•周本纪》记载：“（武王）封尚父（姜子牙）于营丘，曰齐。”这反映了当时实行的政治制度是（　　）

在做“探究影响电流做功多少的因素”实验时，可以根据灯泡的亮暗程度比较相同时间内电流做功的多少．如图是进行该探究的电路之一．

Boys and girls,

Attention, please! Do you know 1to keep safe in our daily（日常的）life? Today I’d like2 you some ways to keep safe.

1  Always play in a 3 place. A park is a safe place4 there are no cars or buses in it.

2  5 the traffic rules, please! Before crossing a road,6 and look both ways ——look left, look right and look left 7.

3  Never put your head or hands 8 a car, a bus or a train. Many people get 9 or lose their lives by doing so.

4  Don’t 10 a stranger（陌生人）or go with him/her.

That’s all. All the students should obey the rules anytime(任何时候).

“物竞天择，适者生存”是下列哪部著作中提出的思想(    )