There are 500 students in our school,45% (of whom)are boys.为什么要填"of whom",而不是"of them"

are you a studen的单数形式 英语阅读题 100分There are four people in the twins’ family .They are the twins,their father and their mother.The twins’ names are Lucy and Lily.They are fourteen.They are in the same class in the NO.1 Middle School.They are very good studen 1.there are a flowers near the river.（改为一般疑问句）2.there is a clean river in the park.(用a dirty river改为一般疑问句）3.it;s time to have lunch.(改为同义句）t;s time .4.i am an university studen.( ) 5.are your principal 英语题（句子改错）很简单的1.The shop assistant asks Mrs Brown what she want.2.There are three America girls looking after the old woman.3.How much potatoes does the cook want?4.I must give her medicine in the right time.5.A lot of studen the micro blogs in China are popular with young people,especially we studets!为什么不用our studen There are There are there are are there 还是there are 英语句子适当形式填空 1 The studen are（ ）（write）in the classroom 2The players are （ ）（run）outside many a studen and teacher work in groups.one studen there are=there're There are some ---(German)there. -What are ______over there?-There are boxes. there are still 还是 there still are there are some 还是there are two 用there are 造句