已知集合U={1,2,3,4,5,6,7},集合A={2,4,5},则∁UA=( )
A:∅
B:{1,3,5}
C:{1,3,6,7}
D:{1,3,5,7}
Little Leo worked hard and a great artist.
尿的生成虽然是连续的,可尿的排出是间歇的,这是因为( )