问题 解答题

一布袋中有红、黄、白三种颜色的球各一个,它们除颜色外其它都一样.小亮从布袋中摸出一个球后放回去摇匀,再摸出一个球.请你利用列举法(列表或画树状图)分析并求出小亮两次都能摸到白球的概率.

答案

画树状图得:

∴一共有9种等可能的结果,

小亮两次都能摸到白球的有1种情况,

∴小亮两次都能摸到白球的概率为

1
9

单项选择题

In the United States, the first day nursery was opened in 1854. Nurseries were established in various areas during the (91) half of the 19th century; most of (92) were charitable. Both in Europe and in the U. S. , the day-nursery movement received great (93) during the First World War, when (94) of manpower caused the industrial employment of unprecedented numbers of women. In some European countries nurseries were established (95) in munitions (军火)plants, under direct government sponsorship. (96) the number of nurseries in the U.S. also rose (97) , this rise was accomplished without government aid of any kind. During the years following the First World War, (98) , Federal, State, and local governments gradually began to exercise a measure of control (99) the day nurseries by (100) them and by inspecting and regulating the conditions within the nurseries.
The (101) of the Second World War was quickly followed by an increase in the number of day nurseries in almost all countries, as women were (102) called upon to replace men in the factories. On this (103) the U. S. government immediately came to the support of the nursery schools, (104) $6,000,000 in July, 1942, for a nursery school program for the children of working mothers. Many States and local communities (105) this Federal aid. By the end of the war, in August, 1945, more than 100,000 children were being cared (106) in day-care centers receiving Federal (107) Soon afterward, the Federal government (108) cut down its expenditures for this purpose and later (109) them, causing a sharp drop in the number of nursery schools in operation. However, the expectation that most employed mothers would leave their (110) at the end of the war was only partly fulfilled.

A.Because

B.As

C.Since

D.Although

单项选择题