网络购物方便、快捷，受到人们的青睐，目前我国网络购物用户规模突破1亿。2011年是“网络购物年”，网购交易额超过5亿.国家维权网调查结果显示，网购是2011年发生的侵犯消费者权益的典型行业之一。材料告诉我们(　　)

①消费者应该提高安全防范意识

②网络应用是一把双刃剑，弊大于利

③网络交往对象具有虚拟性、间接性和隐蔽性的特点

④一些网购行业侵犯了消费者的知情权、公平交易权

有一串分数，$\frac{1}{1}$，$\frac{1}{2}$，$\frac{2}{2}$，$\frac{1}{2}$，$\frac{1}{3}$，$\frac{2}{3}$，$\frac{3}{3}$，$\frac{2}{3}$，$\frac{1}{3}$，$\frac{1}{4}$，$\frac{2}{4}$，$\frac{3}{4}$，$\frac{4}{4}$…请问$\frac{7}{10}$是第几个分数？第400个分数是几分之几？

A：What do you want to be____?

B：____

A：Why? Many students don't like their teachers.

B：Because my grandma is a teacher. She is very friendly, and her students all love her very much.

A：I think____

B：Thanks. What about you?

A：____like Brad Pitt(布拉德•皮特).

B：Wow, he is very smart and cool. I like his films very much.

A：Yeah. ____these days. I hope my dream can come true one day.

B：Good luck!