4.Most of the large cities in the world have grown without plans, which London is a such one.
解析：此题为五星级题。在which 之前加among. which 引导了非限制性定语从句，先行词为the largest cities,所以定语从句应为：London is a such one among most of the largest cities. 故应在which 之前加介词among。
e.g. He bought a computer, for which he paid 5 000 yuan.
In the distance there are a lot of students, one of whom is an old friend of mine.
