截至2016年底，某市人口总数已达到7250000人，将7250000用科学记数法表示为（   ）

①往Na₂SiO₃溶液中通入CO₂产生白色沉淀

②石墨是导体，晶体硅是半导体

③制玻璃过程中发生反应Na₂CO₃+SiO₂ $\underset{\_}{\underset{\_}{高温}}$  Na₂SiO₃+CO₂↑

④CH₄比SiH₄稳定．

It is August 2050. Mrs Peng and Mr Yu are writing about hotels and houses on their posts.

The Hotel Whale

  The Hotel Whale is built (A) 在水下. It is in the shape of a whale. This hotel has 50 bedrooms, a cafe and a shopping centre.

Mrs Peng: “When we were staying at the hotel recently, my children watched the fish outside their bedroom window. (B) They were never bored.”

Forever Green Houses

  These houses are both “green” and “smart”. There is glass outside the houses. Heat is held under the glass and is then used as energy for (C) each house. In the bathroom, your medicine cupboard is connected to your doctor’s computer. In the kitchen, your smart fridge tells the supermarket’s computer when you (D) need more food.

Mr Yu: “When we were living in our old house, we were using more energy. I would certainly recommend Forever Green Houses to my friends. (E) They will satisfy everyone.”