电场正、负极间距愈大,除尘效率愈高。
参考答案:对
20世纪六七十年代,为促进教育机会均等,英国工党政府将文法学校、技术中学和现代中学合并组建成新型中学。这种中学是()。
A.完全中学
B.统一中学
C.综合中学
D.文实中学
Not until he left his home _____ to know how important the family was for him.
A.did he begin
B.had he begun
C.that he began
D.he had begun