对如图的四种动物按照由低等到高等的顺序排列，其中排序正确的一组是（　　）

A．甲、乙、丙、丁

B．甲、丁、乙、丙

C．甲、丙、丁、乙

D．丁、甲、乙、丙

Though Sundays are ______ as a day for rest, we must make good use of them.[ ]

A. set out    

B. set down    

C. set aside    

D. set off