题目

下列反应一定属于氧化还原反应的是（ ）A.化合反应 B.分解反应C.置换反应 D.复分解反应 答案：【答案】C【解析】A．化合反应不一定为氧化还原反应，如氧化钠和水的反应，故A错误；B．分解反应不一定为氧化还原反应，如碳酸氢钠的分解，故B错误；C．置换反应有单质参加，一定存在元素化合价的变化，为氧化还原反应，故C正确；D．复分解反应一定不是氧化还原反应，故D错误。故选C。看图填空，一空一词。1. What can you see in the picture?     We can see that a school ______ ______ a skating Marathon. 2. How many people are there in the picture? And who are they?    There are seven. Five are students and the ______ of them are ______. 3. What are the they doing?     A man and a woman are ______ Alison, most students are skating and two of them     are ______ on the ground. 4. What is Alison doing?     He is ______ the woman's ______. 5. When did Alison started skating?     He started skating ______ hours ______.