岩石圈是指（　　）

$\frac{1+2i}{{\left(1-i\right)}^2}=$（　　）

生命活动是神奇而复杂的，从某种程度讲，它依赖于生命所特有的结构层次．下列关于一株苹果和一只青山羊的叙述中不正确的是（　　）

如图，长为2l的直导线折成边长相等，夹角为60°的V形，并置于与其所在平面相垂直的匀强磁场中，磁感应强度为B．当在该导线中通以电流强度为I的电流时，该V形通电导线受到的安培力大小为（   ）

B

    I'm at Billy's birthday party. There are a lot of friends in his house. Some stand beside the table and enjoy the snacks and drinks. There is some food on the table. I like the chocolate and the fruit very much. Billy sits in the sofa and chats with some friends there. He wears a red T-shirt and a pair of blue jeans. He looks so cool today. Wow! The cake is really big. There are some candles on it. Billy's friends begin to sing 'Happy Birthday' to Billy. Billy is very excited. He blows out the candles (吹蜡烛) and cuts the cake. Everyone has fun at the party.