A:甲是固氮微生物,乙是自养微生物,丙是异养微生物
B:甲是异养微生物,乙是固氮微生物,丙是自养微生物
C:甲乙都是自养微生物,丙是异养微生物
D:甲乙丙都是异养微生物
读“大气垂直分层示意图”回答“蓝蓝的天上白云飘”,歌词中的蓝天白云发生( )
I ______ have worried before I came to the new school, for my classmates here are very friendly to me.