A:(-1,0)
B:(-∞,0)∪(1,2)
C:(1,2)
D:(0,2)
造成很多同学学习时间不够的原因有( )①做事拖拉,事情越积越多②按部就班的实现制定的学习目标③没有制定学习计划,做事太随意④没有体会到学习中有苦更有乐
Tom has to go to school every day because his parents are too busy to take him to school.
下列关于声音的说法正确的是( )