阅读下面材料，在空白处填入适当的内容（不多于1个单词）或括号内单词的正确形式。
Nowadays, more and more schools in China have rules making students wear school uniforms to school. A lot of Chinese students complain about____ (wear) their school uniforms every day. But do American students get ____(annoy) about their uniforms, too? American high schools usually have a dress code(衣着标准), ____ is about requirements for students' dressing. Boys at school must wear clean jackets every day. Girls are ____ (luck) than boys, for they have more flexible____ (choose) than boys. They can either dress similarly to the boys ____wear a dress. In general, it takes a student 10-15 minutes every morning ____ (dress) up for class. As students do in China, plenty of American students also have their complaints about school uniforms. What if students really dislike the dress code and want to get rid of it? Instead of getting punished, ____ (actual) there're ways to do that. At my school, "dress down" tickets ____ (sell) on school days. If students are willing to buy a ticket, they don't need to wear school uniforms the following day. I have a strong ____ (believe) that one day Chinese students can buy these tickets, too.
，其中η＝l．8×10-3Pas，血浆的密度为ρ1＝1．0×103kg/m3．红血球的密度为ρ2＝1．3×103kg/m3．则估算红血球半径的大小为 （ ）