阅读短文，下列问题

  Solve equations(方程式)and fun number problems with this online Maths game for kids. Understand how to do mental (只在心里做的) Maths, train your brain to handle (处理) numbers and improve your problem solving skills.

    If you want to improve your multiplication skills, then give this great activity a try.

    Follow the instructions and solve a range of interactive multiplication problems that are perfect for kids.

    Check out this cool division game for kids. Have fun improving your math skills with a variety of interactive challenges.

    Click on the flashing signs as they show the correct answer, watch carefully and don't click on the signs too early, can you finish them all?

    This place value game for kids helps children understand how units of numbers work.

    Complete fun activities, number problems and simple equations while learning about tens, hundreds and thousands.

阅读下列材料，按要求作答：

人类在生产和生活中排放的废水、污水和废物是赤潮生成的关键，它们汇聚到海洋中，在温度、盐度适宜，海水稳定的情况下，赤潮生物迅速繁殖，形成赤潮．大量海洋生物窒息死亡或被毒死，并通过食物链危害人类健康；海洋生物的光合作用受阻，海洋食物链受到破坏．我国海域在20世纪50年代以前仅有3次赤潮，60年代1次，70年代9次，80年代29次，90年代后，急剧猛增，仅1990年就发生了34次．

2017年4月1日，河北雄安新区成立。雄安新区是中国第19个国家级新区。按照规划，它将成为绿色生态宜居新城区、创新驱动发展引领区、协调发展示范区、开放发展先行区。对此理解正确的是（    ）

①改革开放是立国之本

②新区将实行资本主义制度，高度自治

③可以缓解京津两地的人口、资源、环境压力

④我国坚持“创新、绿色、协调、开放、共享”的发展理念