下列关于商鞅变法的历史条件表述正确的是(　　)

①秦国是战国七雄中相对落后的国家　②当时秦国国君希望变法图强　③秦国贵族认同了商鞅的变法主张　④战国时期各国纷纷变法形成变法潮流

Jim：Hi, Kate！What's the weather like in Shanghai today?

Kate：Hi, Jim！It's sunny and warm here. I'm going to the zoo this afternoon.

Jim：Sounds good.

Kate：Jim, how's the weather in Beijing now?

Jim：It's cloudy. It's going to rain. So I can't fly a kite in the park.

Kate：Oh, I see.

Jim：Do you know the weather in Guangdong?

Kate：It's too hot. The children there usually go swimming in the river.

Jim：Oh, I like swimming, too. But I can't swim now. It's cold here.

设击球点的高度为2.5 m，问球被水平击出时的速度v在什么范围内才能使球既不触网也不出界？

直线经过点A（2，1），B（1，m²）两点（m∈R），那么直线l的倾斜角取值范围是（    ）