题干
What are people supposed to do when they meet for the first time in China?（ ）
A：
B：
C：
答案(点此获取答案解析）
B
What are people supposed to do when they meet for the first time in China?（ ）
A：
B：
C：
2HNO3＋4N2＋9H2O，在反应中被氧化与被还原的氮原子数之比为（ ）
