计算3﹣2.75+ $\frac{1}{2}$ 时，比较合理的方法是（　　）

    I'm crazy about chocolate, so it's no surprise that my favorite book is Charlie and the Chocolate Factory by the wonderful Roald Dahl. Forget Charlie Bucket, the real hero is Willy Wonka, inventor of the most amazing sweets in the world.

    Here are just a few of his delicious creations ：

    Hot ice cream for a cold day! What a great idea. Now I can eat ice cream every day! He also invented an ice cream that never melts (融化）—very useful.

    Wallpaper that you can lick. This wallpaper comes in orange, grape, apple and banana flavours. When you lick the pictures, you taste the fruit. Brilliant!

    Grass made of sugar called Swudge. It grows by the chocolate river and the chocolate waterfall in Willy Wonka's factory.

    Mr. Wonka also invented some special sweets for schoolchildren, such as a kind of chocolate others cannot see when you are eating it. There are also sugar-coated pencils and magic hand-fudge (软糖）—you hold the fudge in your hand and you taste it in your mouth. Finally, there are Wonka's exploding weets — a great way of scaring (恐吓）the school bully!

    Anyway, these are just a few of his inventions. Read the book if you want to know more.

在建国后一段相当长的时期内，我国城市居民购买粮、布、油都要凭票。1983年12月1日，商业部通告全国：敞开供应棉布，取消布票。从此，自1954年9月9日开始使用的布票成为历史文物。这些政策说明

①中国经济的发展与国家政策都发生了很大的改变 ②政府不再单纯以行政手段调配资源

③中国逐渐由计划经济向市场经济过渡 ④已经建立了社会主义市场经济体制