“牛肝地”是指在红层软岩分布地区形成的以密集侵蚀沟和风化壳裸露为标志的类似荒漠景观的土地。下图示意位于我国某区域“牛肝地”形成过程中不同演替阶段下的植物群落与土壤特征的变化。据此完成下列各题。

    I am Kate. I am a girl from New York.

    Today is Sunday. My1don't go to work, so they go to 2 their friends. I am3home alone. After I finish my homework, I'm4So I ask some of my friends to my 5and have fun.

    It's half past ten6the morning now. We are7diffrenet things. Look! Jack is playing computer8Someone may think it is 9 but Jack likes playing them. I am 10 some music on my MP3.11is Lisa doing now? Oh, she is 12to the music. She can dance very well. She 13to be a dancer when she grows up. As for Alice, she is14a newspaper on the sofa. We 15all having a good time.

①人体内部的磁场与地磁场相比很弱，若用磁感线描述人体内部的磁场和地磁场，则下列判断中合理的是____（选填：a、b或c）．

A．人体内部磁场的磁感线分布较疏

B、人体内部磁场的磁感线分布较密

C、两者磁场的磁感线疏密大致相同

②对人体内部磁场存在的原因提出猜想，请写出一种猜想及其依据．____．