如果仅从地面热力作用的影响考虑,一天中空气最新鲜的时段出现在( )
A:清晨
B:中午
C:傍晚
D:夜晚
—How many people were invited to the meeting?
—About six ________.
如图这朵花的哪一部分被摘除后,它将一定不能结果( )