这几个问题问得很好!
1.Life is hard at high altitude,and the mountains make communications difficult.
其中的difficult补充说明宾语communications,充当宾语补足语.此外,动词不定式也常和前面的宾语一起构成复合宾语,其中的不定式充当宾语补足语.
目的状语、宾语补足语和后置定语有时难以区分,请对比分析下面三个短语,你就很清楚啦!
use sth.to do 用某物做某事,此处"to do”是修饰"use sth."整体的,做目的状语；
ask sb.to do叫某人做某事,"sb."与"to do"存在逻辑上的主谓关系,故"to do"用作宾语补足语：
sth.to eat可以吃的东西,"to eat"与"sth."存在逻辑上的动宾关系,故"to eat"用作后置定语.
2.Every morning he climbs up to the bend with a large circular board in his hand.
英语中由“with (without)+宾语+宾语补足语”构成的复合结构也可视为一种独立主格结构,其中的“宾语”通常由名词或代词充当,但代词一定要用宾格而不能用主格
(1) with / without + 名词或代词 + 形容词
Don’t sleep with the windows open.别开着窗睡觉.
(2) with / without + 名词或代词 + 副词
He stood before his teacher with his head down.他低着头站在老师面前.
He left the office with the lights on.他离开了办公室,让灯亮着.
(3) with / without + 名词或代词 + 介词短语
She came in with a book in her hand.她手里拿着一本书走了进来.
He spoke to us with his mouth full of food.她口里含着食物跟我们说话.
(4) with / without + 名词或代词 + -ing分词
Don’t brush your teeth with water running.不要在刷牙时让水流着.
He fell asleep with the lamp burning.他没熄灯就睡着了.
I won’t be able to go on holiday with my mother being ill.因为妈妈有病,我无法去度假.（作原因状语）
(5) with / without + 名词或代词 + 动词不定式
I can’t go out with all these clothes to wash.要洗这些衣服,我无法出去了.（作原因状语）
With so much work to do,the manager felt very worried.这么多工作要做,经理觉得很焦急
(6) with / without + 名词或代词 + 动词的过去分词
He sat there with his eyes closed.他闭目坐在那儿.
All the afternoon he worked with the door locked.整个下午他都锁着门在房里工作.
3.But often they just pass by,taking the human traffic signal for granted.
这句话中的"taking the human traffic signal for granted”是现在分词做方式状语,又如：
The children ran out of the room,laughing and talking merrily.
