We have twenty minutes' rest between classes. Look! Most of us are playing during the break time. Some students are on the playground. They are playing basketball. Oh! A boy is running with the ball. And another is trying to stop(阻止) him. They look so cool. And there are some girls watching the game. Some students are in the classroom. They are talking. A few of them are reading and doing homework. Look!  A girl is looking at the birds in the tree in front of the classroom. She must be thinking of something interesting because she is smiling. What are the teachers doing? Some of them are working in the office. And some are talking with students. Everyone is doing his or her things. They are busy but happy.

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钙元素属于____（填“金属”或“非金属”）元素，相对原子质量为____，其元素的原子在化学变化中容易____（填“得到”或“失去”）电子形成离子，离子符号为____

作为新事物的电动汽车，其绿色环保且使用成本低，但仍然未受消费者喜爱，最重要的原因在于“里程焦虑”。只要续航里程低于50公里，驾驶者就有“赶紧充电”的焦虑，而这佯的“里程焦虑”几乎是每个电动汽车使用者的心态。从材料可以看出（    ）

①电动汽车市场的发展前景令人担忧     ②电动汽车存在着弱点和不完善之处

③电动汽车市场的质变有待量的积累     ④电动汽车的推广过程不会一帆风顺

农业生产的布局往往因城市而发生变化，距城市远近距离的不同，也往往形成不同的农业生产类型。下图为我国某大平原地区大城市周围农业生产布局示意图，该平原地区大面积种植冬小麦。读图，城市外围甲、乙、丙、丁布局的农业生产合理的是（    ）