A. 请根据句意或括号中的中文提示、英文释义，写出句中所缺单词，使句子通顺。 
My cousin is studying in Beijing, so we _________(not very often) see each other now.
—Where’s your mother?
— She is in the ________(厨房) cooking a meal.
We should try our best to prevent water ________(the state of being dirty) because people can’t live without water.  
The weather report said that the temperature would fall _________(在……下面) zero.
We all know that _________is between June and August.