英语造句时，不应使用不必要的词。只要意思得到完全表达，那么所用的词应该是越少越好。
原句：In China, some cities are seriously polluted, and some cities are being polluted.
优化：In China, some cities are seriously polluted, some being polluted.

原句：She likes collecting stamps which is her hobby.
优化：Collecting stamps is her hobby.

原句：Gone with the wind was a good film which I enjoyed watching very much.
优化：I enjoyed watching Gone with the wind very much