A:﹣1
B:0
C:﹣2
D:12
读“中国地图”和“京津唐地区图”回答下列各题:
The teachers encourage their students to the problems by themselves, and in this way students can enjoy success.
把一段带叶的茎下端插入装有稀释红墨水的瓶子里,放置在温暖的阳光下,待到叶脉微红时,用肉眼观察茎的横切面,染红的结构是( )