快考试了,像高人求救and表并列的三种形式的区别！！！

拜托各位了，一遇到and的题我就蒙了，麻烦给我区分一下这几种形式有什么区别，都应该怎么用呗~~

1，most of the purported health benefits of tea come from antioxidants-compounds that arealso found in beta carotene,vitamin E,and vitamin C and that inhibit he formation of plaque aling the bodys blood vessels.

2,Australian embryologists have found evidence to suggest that the elephant is descended from an aquatic animal and that its trunk originally evolved.

(不明白为什么and后面要加that,它指什么，和谁并列啊？)

3,Many environmentalists,and some economists,say that free trade encourages industry to relocate to countries with ineffective or poorlu enforcd antipollution laws,mostly in the developing world,and that,in order to maintain competitveness,rich nations have joinde this downwaid slide toward more lax attitudes about pollution.

（这个也一样不明白为什么要有“，”）

4，Part of the proposed increase instate education spending is due to higher enrollment:number of students in public schools has grown steadily since the mid-1980s and,at nearly 47million,has reached.

第2个，suggest that....and that...并列