His parents are very concerned about his son at school because he _______moving in his seat.

A．is always keeping

B．always keeps

C．does keep

D．has always kept

若发现已生效的行政执法行为违法或不当，则( )。

A．原行政机关无权废止

B．原行政机关或上级行政机关有权撤销

C．只有权力机关有权撤销

D．相对一方当事人有权变更