根据材料内容，选择正确答案。

    By about 2020 a new company from India will be opening dollar stores all over the world to sell their products. They will be a huge success, selling a lot of big things for low prices.

    At these stores, they will sell a car that is customized(定做) to the customer's needs. So you will buy your car piece by piece. What's the point of buying a top if you don't need one? Why buy sides to your car if you want a good view? If you always drive alone, what's the point of buying four seats? The solution is to buy only what you need; pay a dollar for each wheel, a dollar for the engine, a dollar for the floor, a dollar for a seat, and away you go. When it looks like rain, run back and buy a roof.

    When winter comes you can buy the sides and top; or fold up what you have and store it. Reliability(可靠性) won't be a problem because when something breaks down, just throw it away and buy a new one. When you get tired of the color of style, just replace it. While it may feel like you are always dishing out money, by the time you've done, you might only pay $12.00 for the entire car, so let's not complain.

    This store will be such a big hit in India.

设a,b是两条不同的直线，$\alpha ,\beta$是两个不同的平面，则下列四个命题中，正确命题的个数是（   ）
①若 $a\perp b,a\perp \alpha$,则$b\parallel \alpha$ 

②若$a\parallel \alpha ,\alpha \perp \beta$,则$a\perp \beta$
③若  $a\perp \beta ,\alpha \perp \beta$，则$a\parallel \alpha$

④若$a\perp b,a\perp \alpha ,b\perp \beta$，则$\alpha \perp \beta$

工业废水中含有硫酸亚铁、硫酸铜和污泥．某同学设计了利用废水制备硫酸亚铁晶体（FeSO₄•7H₂O）并回收铜的实验方案，流程如下，

回答下列问题：

已知：硫酸亚铁晶体受热易分解．