题干
It's time for ．Let's sing and dance．
A：PE class
B：English class
C：music class
答案(点此获取答案解析）
C
It's time for ．Let's sing and dance．
A：PE class
B：English class
C：music class
，614C的半衰期为5700年，请问：该生物死亡时距今约多少年？
2NH3(g) ΔH<0，达到平衡，当单独改变( )