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问题 填空题
连续掷两次骰子得到的点数分别为m，n，则直线y=
m
n
x与圆x2+（y-3）2=1相交的概率是______．
答案

由题意，直线与圆相交，由圆心到直线的距离小于半径1，圆心（0，3），直线方程为mx-ny=0故有

|3n|
m2+n2
＜1，即8n2＜m2

当n=1时，m可取3，4，5，6；当n=2时，m可取6，故使得直线y=

m
n
x与圆x2+（y-3）2=1相交的种数共5种

连续掷两次骰子得到的点数分别为m，n，所组成的数对的总数为36

故续掷两次骰子得到的点数分别为m，n，则直线y=

m
n
x与圆x2+（y-3）2=1相交的概率是
5
36

故答案为

5
36

多项选择题

吹填区排水口的位置应根据（）等因素确定。

A.排泥管的布置

B.容泥量

C.挖泥厚度

D.吹填区地形

E.排泥总流量
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单项选择题

Few scientific fields are as full of risk as that of research into human intelligence. The two questions that (1) over and over again are "is it a result of nature or nurture" and "does race make a difference"

Making (2) comments about the second question can be a (3) move, as James Watson, a co-discoverer of DNA structure, recently found. He suggested that he was " (4) about the prospect of Africa" (5) "all our social policies are based on the fact that their intelligence is the same as ours (white people) (6) all the testing says not really". Such (7) by Dr. Watson are not merely (8) , they are scientifically weird. If the term (9) has any useful scientific meaning, then Africa, the continent where modern humanity began, is most racially diverse. The resulting (10) among the public forced Dr. Watson to leave his laboratory.

(11) , the study of the first question (12) between intelligence and genetics— has some wiser practitioners. One of them, Terrie Moffitt, of King’s College, has just (13) a project judging the relative importance of nature and nurture. Dr. Moffitt’s team (14) the effect on intelligence of breastfeeding, but in a genetic context. Previous studies have shown that breastfed children are more intelligent, (15) about six IQ points, than those given baby formulas.

The team, however, (16) the involvement of a gene called FADS2, which comes in two varieties, known as C and G. The researchers (17) if these two varieties interacted differently with breast milk. (18) on data from two groups of people, they found that the intelligence increase associated with breastfeeding only happened to people having (19) at least one copy of the C variety. The effect did not. (20) on the social classes or IQs of the parents.

3（）

A.career-killing

B.career-facilitating

C.time-consuming

D.energy-saving
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