理解不正确的一项是（    ）

计算$\frac{1-i}{1+i}$的结果是(   )

B

    It's 14:00. The house is quiet(安静的). "Tom?" Mom says. No one answers.

    Mom comes to Tom's house. He is not in the bed. But his model plane is on the desk. "He is not in his room, and he is not in the yard(院子)," Mom thinks. Then Mom comes to his grandparents' room. Tom likes to play with Grandpa's tape player. But he is not there.

    Mom looks for(寻找) him everywhere. But where is Tom? Mom is worried. She wants to call Dad. She comes to the living room to get the phone.

    "What's that?" Mom sees something(某物) black under the sofa. Oh, it's Paul, Tom's dog. It loves sleeping(睡觉) there. But what is next to Paul? It's Tom!

正常人的体细胞中染色体可分为____ 和____ 。其中和性别决定有关的染色体称为____ 。和性别决定无关的称为____ 。

在电磁学发展史上，提出分子电流假说的科学家是（   ）