题干

我国未来将建立月球基地,并在绕月轨道上建造空间站.如图所示,关闭动力的航天飞机在月球引力作用下向月球靠近,在B处重新点火改变速度至与空间站速度相同,并与空间站对接,已知空间站绕月轨道半径为r,周期为T,万有引力常量为G,下列说法中正确的是(         )

A:图中航天飞机正匀速率飞向B

B:航天飞机在B处由椭圆轨道进入空间站轨道必须加速

C:根据题中条件可以算出月球质量

D:根据题中条件可以算出空间站受到月球引力的大小

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C

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Why I Love Cycling

    One of the first things I did when I moved to a new city was hire a bike. Why?____ You travel much faster than on foot and you notice so much more of your surroundings than when in a bus or a car. It's more appealing to wander down small streets if they seem interesting, as you can quickly get back to the main road.

    Besides, I soon discovered plenty more benefits to cycling.

    A bike means that fewer places, especially in a small city like the one where I live now, feel far away. For example, cycling to work takes me half the time that it would to walk.____

    Of course, there are obvious health benefits of cycling—a bit of extra movement as part of your daily routine can help you keep fit and healthy. Cycling on my way to work also makes me feel more energetic in the mornings.

    ____ While cars pollute the environment, bikes are carbon-neutral. Furthermore, thanks to being petrol-free, bikes are cheaper to run, buy and fix than cars. Even if you don 'town a car, a bike can pay for itself when compared to the price of bus tickets.

    ____ Always wear a helmet, pay attention to other traffic and don't forget your lights at night. Make sure you know the road rules, especially in a new place. Some cities are more cycle-friendly than others.____ Luckily, where I live now is pretty easy to ride a bike around, thanks to having lots of cycle lanes and not too many hills!

A. However, be careful when cycling.

B. I have to learn to ride safely on the right of the road.

C. Importantly, cycling also helps to reduce your carbon footprint.

D. And sometimes city roads are difficult or unpleasant for cyclists.

E. Riding a bike also means you're not restricted by bus timetables.

F. Seeing a city by bike is ideal for settling in and learning your way around.

G. Cycling to work excellently fits for someone who wants to save their pocket money.