1.It takes my mother half an hour to cook dinner for us.
Cooking dinner for us takes my mother half an hour.
Half an hour is spent by my mother in cooking dinner for us.
另外：其中的half an hour都可以改成30 minutes.
不同的写法强调的内容不同.
2.Sweets provide me with energy but they are not good for health.
Sweets can offer me energy,but they are not healthy.
Sweets can make me energetic,but they are unhealthy.
...
这句有很多很多种写法啊= =