当正整数集合A满足:“若x∈A,则10﹣x∈A”.则集合A中元素个数至多有( ) A.7 B.8 C.9 D.10 答案:C【考点】15:集合的表示法. 【分析】由x∈A,则10﹣x∈A可得:x>0,10﹣x>0,解得:0<x<10,x∈N*.若1∈A,则9∈A.同理可得:2,3,4,5,6,7,8,都属于集合A.即可得出. 【解答】解:由x∈A,则10﹣x∈A可得:x>0,10﹣x>0,解得:0<x<10,x∈N*. 若1∈A,则9∈A.同理可得:2,3,4,5,6,715、The new law to punish the drunk driver will come into
on the day it passes.
A.existence
B.use
C.service
D.effect