小红家里使用的是瓶装液化气，每瓶中装入的液化气质量为21kg，液化气的热值取5.0×10⁷J/kg．

（1）整瓶液化气完全燃烧，释放的热量是多少？

（2）若整瓶液化气完全燃烧释放热量的60%被利用，那么散失的热量是多少？

（3）小红想节约能源、降低能耗，若将上述散失的热量全部利用起来，可以把多少千克温度为10℃的水加热到50℃？

一铜块和一铁块，质量相等，铜块的温度T₁，比铁块的温度T₂高，当它们接触在一起时，如果不和外界交换能量，则（   ）

    I have two good friends．They are Gina and Jenny, and they are twin(双胞胎之一的)sisters．They come from Singapore．They are 12 years old．They can speak English and Chinese．

    Now the twins are in China．Their family are in China，too．They live in Shanghai．There are five people in their family．They are their parents，their brother and them．Their mother is a doctor．Their father is a teacher．Their brother Alan is very young．He is four years old．He can't go to school．

    Gina，Jenny and I are in the same class．Every day, we walk to school and talk a lot．They say China is a very good place and they like China．

根据材料内容选择最佳答案。

判断下面的句子是否有毛病。

苏州、杭州、大连、昆明是我国江南旅游胜地。（    ）