为了在四位学生中选拔一名参加数学竞赛，目标是争取获奖，因此对他们的数学成绩分析后得出：四位学生的平均成绩均为96分，甲同学的成绩方差为0.54；乙同学的成绩方差为0.44；丙同学的成绩方差为0.45；丁同学的成绩方差为0.53。则应该选（   ）参加比赛比较稳。      

******在讲话中经常引经据典，展现了中国优秀传统文化里的东方智慧。2015年，他在浙江乌镇举行的第二届世界互联网大会上讲到：“天下兼相爱则治，交相恶则乱。”***主席引用的这一观点出自于（    ）  

    Halloween is a very popular holiday in North America. People celebrate it on October 31st. On this day, many people decorate their houses. Many people like to make jack-o'-lanterns. They are made from pumpkins. Some jack-o'-lanterns are funny and some are scary!

    Children wear costumes and go trick-or-treating to collect candy. Many of these costumes are scary! Witch, ghost, vampire and black cat costumes are popular.