根据短文内容及首字母提示，补全空格内单词，使短文完整、通顺。(请在答题卡上写出完整单词)

    It was sunny and h____ again at this time of year. John went to the beach to s____ his weekend. He was lying on the sand and l____ to music. Suddenly he h____ someone crying for help. He j____ up hurriedly and looked towards the voice. He saw a little boy waving(挥动) his hands in the w____ a little far away. He t____ off his clothes and jumped into the water

    q____ . He swam to the little boy, held him, kept his head a____  the water and swam back to the beach. At last, the boy was safe. He thanked John a l____ .

小红在长跑练习中，离达标总是差那么一点，同学们纷纷鼓励她，你认为最恰当的话是（  ）

在催化剂并加热的条件下，氨气和氧气能发生化学反应，其反应的化学方程式为4NH₃+5O₂ 4X+6H₂O，则X的化学式是

（  ）

下列说法正确的是（  ）