光化学烟雾的定义含有氮氧化物和烃类化合物的大气,在阳光中紫外线的照射下发生光化学反应所生成的臭氧、醛、酮、过氧乙酰硝酸酯等二次污染物的混合物被称为光化学烟雾。
参考答案:对
根据句意和首字母填写单词。
1. I have so many c_____ to do today.
2. He got up at 5:00, c_____ wood and l_____ the fire for breakfast.
3. Then he had to f_____ animals.
4. Please give me a travel g_____.
5. Have you packed the t_____ yet?
冬季气温低时要用黏度()的机油。
A、较大
B、适中
C、较小
D、不变