某烃分子中碳、氢两种元素质量比为5 : 1,且分子中含有3个甲基,则该烃分子的一

题型:选择题

问题:

某烃分子中碳、氢两种元素质量比为5 : 1,且分子中含有3个甲基,则该烃分子的一氯代物共有几种(不考虑空间异构)

A.1

B.2

C.3

D.4

考点:结构简式结构式
题型:选择题

以下对结构体类型变量td的定义中,错误的是( )。
A) typcdef struct aa
int n;
float m;
AA;
AA td;
B) struct aa
int n;
float m;

struct aa td;
C) struct
int n;
float m;
aa;
struct aa td;
D) struct
int n;
float m;
td;

题型:选择题

药物残留溶剂测定法中,按国际上统一划分,苯属于()

A.第一类溶剂

B.第二类溶剂

C.第三类溶剂

D.第四类溶剂

E.零类溶剂

题型:选择题

对闭式喷头应进行密封性能试验,常采用的设备有()。

A、试压泵

B、压力表

C、秒表

D、游标卡尺

题型:选择题
计算下列各题,能简算得要简算.
36×(
1
3
+
1
6
+
1
9
3
5
×
9
10
+
2
5
÷1
1
9
[1-(
1
4
+
3
8
)]÷
1
4
5
26
×25.
题型:选择题

In one sense, we can trace all the problems of the American city back (91) a single starting point: we Americans don’t like our cities very much.
That is, on the (92) of it, absurd. After all, more than three-fourths of us now live in cities, and more are (93) to them every year. We are told that the problems of our cities are (94) more attention in Washington, and scholarship has discovered a whole new (95) in urban studies.
(96) , it is historically true: in the American psychology, the city has been a basically suspect institution, (97) with the corruption of Europe, totally lacking that sense of spaciousness and innocence of the (98) and the rural landscape.
I don’t pretend to be a scholar on the history of the city in American life. But my thirteen years in public (99) , first as an officer of the U. S. Department of Justice, then as Congressman, and now as Mayor of the biggest city in America have taught me (100) too well the fact that a p antiurban attitude (101) consistently through the mainstream of American thinking. Much of the (102) behind the settlement of America was in reaction (103) the conditions in European industrial centers and much of the theory (104) the basis of freedom in America was linked directly to the availability of land and the perfectibility of man outside the corrupt influences of the city.
What has this to do with the predicament of the modern city I think it has (105) to do with it. For the fact is that the United States (106) the federal government, which has historically established our national priorities, has simply never thought that the American city was "worthy" of (107) —at least not to the (108) of expending any basic resources on it.
Antipathy to the city predates the American experience. When industrialization (109) the European working man into the major cities of the continent, books and pamphlets appeared (110) the city as a source of crime, corruption, filth, disease, vice, licentiousness, subversion, and high prices.

A.supporting

B.promoting

C.encouraging

D.inspiring

更多题库