（1）计算：（$-\sqrt{3}$）⁰﹣|﹣3|+（﹣1）²⁰¹⁵+（$\frac{1}{2}$）^﹣1

（2）化简：（$\frac{1}{a-1}$﹣$\frac{1}{a^2-1}$）÷$\frac{a^2-a}{a^2-1}$．

使动脉血变成静脉血的过程是（　　）

阅读理解

    Many people like going shopping at weekends after five days'hard work．Supermarkets are good places for shopping．

    Before you go into the supermarket，get a trolley．Trolleys are usually outside the entrance(入口)．It's good to push your trolley around and take what you want．If you only plan to buy a few things，get a basket．Baskets are usually in the supermarket．You can buy different kinds of things in the supermarket．You can buy fruit and vegetables，meat and fish，bread and cakes，ice cream and magazines．

    There is a big supermarket near my home．My parents like shopping there but my sister Liz and I don't．There'll  be a sale in it on Saturday．My parents are going to buy some carrots and tomatoes．

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