More than 6000 children were expelled（开除）from US schools last year for bringng guns and bombs to school，the US Department of Education said on May 8．
    The department gave a report on the expulsions（开除）as saying handguns accounted for 58 per cent of the 6093 expulsions in 1996—97，against 7 per cent for rifles or shotguns and 35 per cent for other types of firearms．
    “The report is a clear sign that our nation’s public schools are cracking down（严惩）”on students who bring guns to school，“Education Secretary Richard Riey said in a statement．“We need to be tough-minded（坚强的）about keeping guns out of our schools and do everything to keep our children safe．”
    In March 1997，an 11-year-old boy and a 13-year-old using hand-guns and rifles shot dead four children and a teacher at a school in Jonesboro，Arkansas．In October，two were killed and seven wounded in a shooting at a Mississippi school．Two months later，a 14-year-old boy killed three high school students and wounded five in Daducab，Kentucky．
    “Most of the expulsions，56 per cent，were from high schools，which have students from about age 13，34 per cent were from junior high schools and 9 per cent were from elementary schools．”The report said．

阅读下面这首古诗，回答问题。

春日偶成

程  颢

云淡风轻近午天，傍花随柳过前川。

时人不识余心乐，将谓偷闲学少年。

2013年9月16日，巨星云集的2013世界斯诺克上海大师赛正式开杆，丁俊晖率领总共12名中国职业球手亮相，丁俊晖再次获取排名赛冠军，如图所示是丁俊晖比赛的照片，台球在没有被打出时，台球受到的重力和支持力是一对____ （选填“平衡力”或“相互作用力”）．

下列词语中划线字的字音，字形完全正确的一项是（    ）