请高手分析这个句子的结构1.whatareliefitwaswhentheboulderssuddenlydisappeared,givingwaytoastrenchofplainwheretheonlyobstaclewereclumpsofbushes.thanks这句话的意思是：令人深感慰藉的是大石块突然消

Question

请高手分析这个句子的结构
1.what a relief it was when the boulders suddenly disappeared,giving way to a strench of plain where the only obstacle were clumps of bushes.
thanks
这句话的意思是：令人深感慰藉的是大石块突然消失了，随之而来的是一片平原，这里除了一簇簇灌木丛外，别无障碍。
stretch是这个，我写错了
这句话是绝对正确，很肯定
giving way to 是随之而来的意思
stretch是n.连绵

Answer 1

what a relief it was {when the boulders suddenly disappeared
,【giving way to a strench of plain（ where the only obstacle were clumps of bushes）】.}
*it做形式主语,主语是以when引导的后面的句子{}
*【】内是伴随状语,修饰boulders
*（）内是定语从句,修饰plain
*整个句子是以强调句what...it was做主干的