第十二届全国代表大会常务委员会第十五次会议决定，从2016年1月1日起全国范围内统一实施宪法宣誓制度，会议决定各组人民代表大会及县级以上各级人民代表大会常务委员会选举或者决定任命的国家工作人员，以及各组人民政府、人民法院、人民检察院任命的国家工作人员，在就职时应当公开进行宪法宣誓，如图为2016年2月26日，十二届全国人大常委会首次举行宪法宣誓仪式。

阅读材料，运用宪法的有关知识回答：

如图，一段导线abcd位于磁感应强度大小为B的匀强磁场中，且与磁场方向(垂直于纸面向里)垂直．线段ab、bc和cd的长度均为L，且∠abc＝∠bcd＝135°.流经导线的电流为I，方向如图中箭头所示．导线段abcd所受到的磁场的作用力的合力    (　　)

    The sun, the moon and the stars are all in the sky. We see the sun in the day. We see the moon and the stars at night. The sun is a ball. It is bigger than the moon. The sun has a family. It is the biggest in the family. The moon is a ball, too. It is much smaller than the sun. It is smaller than the stars. The light on the moon comes from the sun. The stars look smaller than the sun and the moon. But most of the stars are bigger than the sun. They are very far away from us, so they look small. All day the stars are in the sky. But the light from the sun is too bright. We cannot see the stars in the day.