在我国，公民之所以既是权利的主体，又是义务的主体，是因为

“人间四月芳菲尽，山寺桃花始盛开”，造成这一差异的环境因素是（  ）

为了除去粗盐中的Ca²⁺、Mg²⁺、SO₄^2-及泥沙，可将粗盐溶于水，然后进行下列五项操
作：①过滤　②加过量NaOH溶液　③加适量盐酸　④加过量Na₂CO₃溶液　⑤加过
量BaCl₂溶液。不正确的操作顺序是         （     ）                          

    Mr Black was walking in the forest（森林） He was scared when he heard a terrible noise. But he could not get out of the forest. His friends were waiting for him in a village outside the forest. They would give him a lot of money if he took a tiger to them, or they were going to laugh at him.
    Mr Black liked hunting(打猎). He usually killed some birds and animals. But a week ago, after he drank too much, he called himself a brave hunter. So his friends bet(打赌) him twenty thousand dollars if he could kill a tiger.
    Suddenly, he heard a little noise. He ran to a big tree,and climbed up it quickly.He didn't come down until he saw it was a farmer. He went close to him and asked, “Excuse me, sir.Are there any tigers in the forest?”
    “Yes,” said the farmer. “I saw a lot of tigers' tracks（足迹）about a kilometer north near here.”
“Good!”Mr Black said in a hurry. “Which way is to the south,then?”

已知f（x）是定义在R上的增函数，且f（x+5）＜f（3－x），则x的取值范围为____．