a是放在地球赤道上随地球一起自转的物体，b是在地球表面附近绕地球做匀速圆周运动的人造卫星，c是绕地球做圆周运动的同步卫星，下列判断中正确的是（   ）

到了冬天，杨树和柳树的叶子纷纷落下，而松树、柏树却依然郁郁葱葱，这表明（  ）

巴西“植物墙”有两个方面的价值是____，____​ 。

A: Morning, Tom. You don't look well. ____?

B: Well, I have got a cold. But it's not serious. Hey, Jack, did you see the movie on CCTV 6 last night?

A: No, I didn't. ____?

B: Harry Potter Ⅲ. It was so exciting. So, what were you doing at that time?

A: ____. I'm not good at English, you know.

B: But English is not very hard to learn. ____.

A: Thank you for your advice. ____?

B: It's nearly 7:50. Hurry up, or we'll be late fir school.

我国肉牛生产优势区域的分布格局经历了从牧区到农区的变化过程，、逐步形成了东北、西北、西南和华北平原四大肉牛生产优势区。图2示意我国l980～2011年肉牛产业发展重心的变化。肉牛产业发展重心移动过程中（     ）

①集约化程度加大    ②良种率变化不大      ③圈养比重上升

④在肉类消费结构中，牛肉超过猪肉        ⑤牛肉商品率提高