1. I’ve been swimming since two hours ago. (就画线部分提问)

                                             you been swimming?  

2. She doesn’t want that pen. She wants this one. (改为同义句)

She wants this pen                             that one.

3. He worked here three years ago.（用since three years ago改写句子）

He                             here since three years ago.

4. The weather was very hot yesterday,                  ? （完成下列反意疑问句）

5.Would you mind wearing those old jeans?(改为否定句)

Would you                                    those old jeans?

计算题：

取水样500ml，用四氯化碳萃取定容50.0，已知校正系数X＝47.5Y＝65.6Z＝445，F＝37.9，经硅酸镁吸附后滤出液的吸光度A2930＝0.681；A2960＝0.308A3030＝0.008试求该样品中石油类的含量。