题目

 (1)1个氨气分子__ __。  (2)2个亚铁离子____。 (3)标出硝酸氨中氮元素的化合价___。 答案：NH32Fe2＋H4O3_People can _______ running everywhere. Do you know what ______?A. be seen; happened B. be seen; is happening C. see; happens