1．布袋里有2個(gè)白球，1個(gè)紅球。任意摸一個(gè)會(huì)是（　?。┣?。

2．The Centerville Middle School chess team consists of two boys and three girls.A photographer wants to take a picture of the team to appear in the local newspaper.She decides to have them sit in a row with a boy at each end and the three girls in the middle.How many such arrangements are possible？（　?。?br />Centerville中學(xué)的國(guó)際象棋隊(duì)由兩個(gè)男孩和三個(gè)女孩組成。一名攝影師想為當(dāng)?shù)貓?bào)紙拍攝這個(gè)團(tuán)隊(duì)的照片。她決定讓他們坐成一排，兩端各坐一個(gè)男孩，中間是三個(gè)女孩。這樣的排列有多少種可能性？（　?。?/div>

3．There are 81 grid points（uniformly spaced） in the square shown in the diagram below,including the points on the edges.Point P is the center of the square.Given that point Q is randomly chosen from among the other 80 points,what is the probability that the line PQ is a line of symmetry for the square？（　　）
如圖所示的正方形內(nèi)有81個(gè)網(wǎng)格點(diǎn)（均勻分布），包括邊緣上的點(diǎn)。點(diǎn)P是正方形的中心。若從其他80個(gè)點(diǎn)中隨機(jī)選擇定點(diǎn)Q，那么線PQ是正方形的對(duì)稱線的概率是多少？（　?。?/div>