In Britain，the government，school leaders，teachers and parents all agree that students should wear uniforms．B____ British private schools have their own school uniforms．They think it's i____ for pupils to wear school uniforms．

    School leaders normally decide if pupils will have to wear a uniform，and they a____ decide what it should look like．You know，no students want to wear65．u____ uniforms．

    Everybody wants to wear beautiful uniforms．

    Leaders have to follows the rules，and they c____ just choose anything they like．They have to t____ of the students' feeling and taste．Here are a few f____ leaders should consider．

    ①Cost．This is the first fact they should consider．Their uniforms shouldn't be too e____ because it may cause problems for some families．Not all the families can afford it．

    ②Sexism（性别歧视）．The uniform policy must be equally fair（公平的）for boys and g____．

    ③Cultrues and races．School rules must a____ pupils from all backgrounds to wear a uniform，for example，allowing Muslim（穆斯林）girls to wear an appropriate dress and Sikh（印度锡克教徒）boys to wear a traditional headdress（头饰）．

下列材料中，能用来观察减数分裂的是 （  ）         

   Here are some facts about homes in the United States and the people who live in them. In the early 1990s, about 50% of the Americans own their homes and the rest rent(租) their homes. The rented homes are usually apartments(公寓).
   74% of the people in the US make their homes in or around cities. 26% live in the country. Dogs live in about 40% of all homes in the US. About half that number have cats.
   Families in the US are becoming smaller. On the average（平均）,2.64 people lived in a home in the early 1990s. In 1960, the average was 3.5.
   Half of the teenagers in the US have their own bedrooms.
   An American moves, on the average，twelve times in his or her life. In Japan, a person moves about five times, and in England a person moves eight times.

在一种溶液中加入氯化钡溶液，产生白色沉淀，再加酸，沉淀不溶解，则这种溶液中（　　）