1. 句中的 green 为名词，用作介词 of 的宾语。alive with the sounds of animals 为形容词短语，修饰名词 green。a huge sea of green alive with the sounds of animals 为修饰 jungle 的同位语。

2. a sea of 大量的，大片的

The crowd stood under a sea of brightly coloured umbrellas. 人群站在鲜艳的伞海之下。

The actor looked out from the stage onto a sea of faces. 演员从台上往下看，真是一片人的海洋。

alive with 充满，满是，到处都是

The pond was alive with frogs. 池塘里到处都是青蛙。

The street was alive with the sound of children playing. 街上传来孩子们玩闹的声音，非常热闹。

Ed was alive with happiness. 埃德高兴得眉飞色舞。

3. 句意：

Welcome to the jungle, a huge sea of green alive with the sounds of animals.

欢迎来到这片丛林，这是一片绿色的海洋，处处可闻各种动物的声音。

您好，感恩您的提问。

Green， noun, 意思 the color  of grass and the leaves of most plants and trees. 

 the green of the countryside in spring 春天乡村的青葱翠绿

The room was decorated  in a combination of greens and blues. 这房间是用绿色和蓝色搭配起来装饰的。

a huge sea of green, 浩瀚的绿色海洋， 比喻草树茂盛，一眼望去犹如海洋，满眼是绿色。