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问题 填空题

已知P（3a-9，2a-10）在第四象限，化简|a-3|+|a-5|等于______．

答案

根据题意，P（3a-9，2a-10）在第四象限，

则3a-9＞0，2a-10＜0；

解可得3＜a＜5，

则|a-3|+|a-5|=a-3+5-a=2．

故答案为2．

单项选择题 A1型题

牙骨质与骨组织的不同之处在于（）

A.层板状排列

B.有陷窝

C.能新生

D.无血管

E.有细胞
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单项选择题

"But the doctor can't use just anyone's blood. The donor's blood has to be of a type that won't be destroyed by your blood." This statement means that______.

A．the doctor can't use the donor's blood because your blood can destroy this

B．the doctor has to choose a donor whose blood can not be destroyed by your blood

C．the doctor has to choose a certain type of blood from a donor whose blood will not be destroyed by yours

D．the doctor can choose a certain type of blood from any donors
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