油炸食品中含有一种叫丙烯醛（化学式C₃H₄O）的有毒物质．

已知f（x）是偶函数，且f（x）在0，+∞）上是增函数，如果f（ax+1）≤f（x﹣2）在$x\in \frac{1}{2},1$上恒成立，则实数a的取值范围是（　　）

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    If you often have a cold, headache or backache, there is something wrong with your health. Eating healthy food 1good for our health.
    Tofu（豆腐）, milk, vegetables are healthy for us. Tofu is a kind of traditional（传统的）2food. We often 3 it in China. Now more and more people 4 other countries think tofu is good for health, 5. They also like eating it. Milk is 6  kind of health food. Every day you should  7  one or two glasses of milk.
    It can 8 us strong.
    Vegetables are very important. You should 9 them. There are vitamin(维他命) A, B, C, D , E and so on in them.
    As we know, it's important10 a balanced diet(均衡饮食). We must have the right kinds of food. We should also eat some pork, chicken and beef. We should eat more fruit and vegetables but less meat.

血浆中的水来自（    ）

       basketball is a good way to make us strong.