229.Prices fluctuate, in response to harvests, natural disasters and political instability; and when they rise, it takes some time before new sources of supply become available.
价格由于收成、自然灾害和政局的动荡而波动；当价格上升时，得过一段时间后才会出现新的供应源。

六级词汇讲解:

本句的主干是Prices fluctuate...; it takes some time...。其中，in response to引导原因状语；before引导时间状语从句。

fluctuate意为“波动，变动”。本句中的in response to为固定短语，意为“作为对……的回应”。如：
He only shrugged his shoulders in response to the question.
他只是耸了耸肩，作为对问题的回答。

instability意为“不稳定；不安定”。如：
The riot can be considered a symptom ofpolitical instability.
这次暴动可以看做政治上不稳定的征兆。