The First Robotics Competition (FRC) was held in Shenzhen. A total of 35 high-school student teams from China, the United Kingdom, Turkey, Poland and other countries joined the two-day contest with their hand-crafted robots.

    The FRC is a world-class robotics competition that was first launched in the United States in 1989. It encourages students to improve their hands-on skills and creative capabilities.

    There are strict rules, limited resources and an intense six-week time limit before the competition. Teams of student should raise money, design a team brand and improve their teamwork skills, as well as build industrial-size robots to compete. The rules of the game include two groups, and each group has three teams. The group with the highest score wins the game.

    The seven teams who won the top prizes in the FRC  Shenzhen Regional will take part in the First Championship to be held in the United States next month.

    Yin Shifei, secretary general, said the competition not only enables students to improve their programming, decision-making and problem-solving skills, but also encourages them to cooperate and share with other people

    According to Yin, a Shenzhen team invited over 40 left-behind children to the city to watch the FRC game because they wanted to make education more equitable. And the left-behind children can get fair education. These children's parents are migrant workers in Shenzhen, but they are left behind i their hometowns.

    Shenzhen became the first city to host an FRC region in Asia last year, and another regional contest will be held in Shanghai this year.

已知a,b为两条不同直线，$\alpha ,\beta$为两个不同平面，且$a\perp \alpha ,b\perp \beta$，则下列命题中不正确的是(    )

下列有关哺乳动物胚胎发育和胚胎工程的叙述，不正确的是（    ）

如图所示，有一固定的且内壁光滑的半球面，球心为O，最低点为C，在其内壁上有两个质量相同的小球（可视为质点）A和B，在两个高度不同的水平面内做匀速圆周运动，A球的轨迹平面高于B球的轨迹平面，A、B两球与O点的连线与竖直线OC间的夹角分别为α=53°和β=37°，以最低点C所在的水平面为重力势能的参考平面，则（sin 37°= $\frac{3}{5}$ ，cos 37°= $\frac{4}{5}$ ）（   ）