按英语语法书的说明：非限制性定语从句只不过对先行词的补充说明，是可有可无的，即便去掉，也不会干扰意思的表达。如：
I do a lot of walking, which keeps me fit. 我常常走路，这使我维持身体健康。
I poured him a glass of wine, which he drank at once. 我给他斟了一杯葡萄酒，他立刻就喝了。
He said that he had never seen her before, which was not true. 他说他从没见到过她，这是虚假的。
We told him to consult the doctor, which advice he took. 大家叫他去看大夫，他听取了大家的劝告。
I cleaned my shoes, which was better than doing nothing. 我把鞋子擦干净了，这比闲着什么都不干要好。
非限制性定语从句的翻译一般有两种办法，一种是后置法（马上非限制性定语从句翻译成并列分句或独立分句，跟在主句后面），另一种是前置法（即翻译成前置定语，即翻译成“……的……”）。你的例句使用的都是后置法，下面列举一些翻译成前置定语的例子：
非限制性定语从句可以翻译成前置定语的，特别是当定语从句比较简短时一般使用此翻译办法。如：
The river, which flows through London, is called the Thames. 这条流经伦敦的河叫泰晤士河。
They went off to swim in the pool, which was now deserted. 他们去一个已废弃的游泳池游泳。
He was already asleep in the bed, which smelled faintly of mildew. 他已经在略带霉味的床上睡着了。
The poem, which appeared in 1890, is an exaltation of married love. 写于1890年的这首诗是对婚姻爱情的高度颂扬。
Happiness, which had been so elusive in Henry’s life, still evaded him. 亨利日常过去一直很难捕捉的幸福仍旧与他无缘。
