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问题 选择题
在式子：
1
a
，
2x
π
，
a2
a+b
，
x
2
，
2
x
+x，
a
a-1
，
x2y3
3xy
中，分式的个数是（　　）
A．2B．3C．4D．5
答案

2x
π
，
x
2
的分母中均不含有字母，因此它们是整式，而不是分式．

1
a
，
a2
a+b
，
2
x
+x，
a
a-1
，
x2y3
3xy
的分母中含有字母，因此是分式．

故选D．

填空题



As crime skyrockets in many communities, people are finally beginning to look for long-lasting effective answers to stem the tide of juvenile crime. Reaching the youth who have committed a crime before they become (1) is an essential step in reversing the crime trend. One (2) may be the establishment of teen court. Teen court is known as a sentencing court for youths who have (3) . Teen courts primarily deal with first-time offenders. After arrest, the young offender must (4) to the charge in juvenile court. With (5) , the offender agrees to be sentenced and abide by the decision of peer jury (6) . Another essential component to teen court is that, as part of the sentence, the offender must sit in on one of more future peer juries to (7) for other offenders. For example, a county teen court in Illinois gives young offenders a chance to (8) their arrests from their permanent record by (9) or other duties ordered by the court. Teen court is not a trial court. All teens admit their guilt and (10) a sentence given to them by a jury of their peers. A judge is present to (11) of the court. The teen court alleviates the strain on the (12) and has been implemented in (13) since the first teen court opened in Odessa, Texas. Beside giving the offender a second chance, it gives the youth (14) in the judicial process.
The purpose of the teen court, aside from sentencing youth offenders, is to (15) both the offenders and the teen volunteers while simultaneously promoting (16) between defendants, the community, and the police. By offering this (17) system, teen court allows those teens who have made a bad decision an opportunity to (18) and learn from it. At the same time those teens learn (19) . The police, the community, and the (20) .
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单项选择题

成人失钾最主要的途径是（）

A.经胃失钾

B.经小肠失钾

C.经结肠失钾

D.经肾失钾

E.经皮肤失钾
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