45．They were spurred by the inflation of the 1970's，which，combined with California's rapid population growth，pushed housing prices，as well as rents, to record levels．

(which引导非限定性定语从句)

它们受到了20世纪70年代通货膨胀的刺激，这次通货膨胀与加利福尼亚人口的迅速增长结合在一起，将房价与租金推到了创纪录的水平。

分句1：They were spurred by the inflationof the 1970's

分句2：which，combined with California's rapid population growth

分句3：pushed housing prices，as well as rents, to record levels

分句1是整个长句子的主句

分句2是分句1的定语从句，修饰inflation

分句3同样是分句1的定语从句，主语仍然是上一句中的which

1和2、3嵌套

2和3并列