The time and effort he has evoted during the pas few years--

A
首先,我帮你分析下句子结构
主干是 The time and effort is now considered to be of great vaule 时间和努力,现在被认为有巨大的价值（ 我这是直译的,方便你看清楚）
he has devoted during the pass few years___trees in that remote area 是修饰主语The time and effort 的
所以做这个题目的时候,你只需要把修饰部分拿出来就容易做了
devote to doing sth 奉献,投身于
在具体点就是修饰部分句子的成分分析：
during the pass few years 是时间状语,可以放在句子最前面,或者后面,甚至暂时不看,都不影响句意,所以这里不看,就变成了he has devoted ___trees in that remote area during the pass few years
这就更容易填啦
所以碰到长句子就先自己分析下句子结构,叫你填的是主干,就看主干,联系枝干（从句）看,
如果要填的是枝干（分句）就拿出来看