题目

 They suspected that the secret had been _____ by one of their friends. A. given off   B. given in   C. given out    D. given away 答案：D化学用语是学习化学的基本工具。请用化学符号或化学式填空：（1）2个氢原子_________；（2）地壳中含量最高的金属元素__________；（3）天然气的主要成分_________；（4）硝酸铵的阴离子__________。