15分英文文法問題

I believe so：我相信是這樣
The world is going mad意思就是：世界就快癲狂

而你兩句的句子文法都不大正確：
but most of the amercian still dosen't know who i am

most在這裏解大多數，既然是大多數，就不是單數，故動詞也要對應用複數形，因此正確是：
but most of the American still don't know who I am.

而I had never hear a voice like that in my life，除了hear應改為heard之外，你所用的時式是過去完成式(past perfect tense)，past perfect tense是以另一個過去的時間作為基準（參考點），而你的句子並未出現這個過去的時間，所以，是以現在為基準時間（所謂現在，是說話者的現在），故要用現在完成式(present perfect tense)，所以，句子應改為
I have never heard a voice like that in my life.

希望幫到你！

2008-06-08 14:32:35 補充：
關於most，yahoo字典也有一例

2. 大部分,大多數[(+of)]
Of course most of them don't agree with his opinion.
當然,他們中大多數人都不同意他的意見。

而Cambridge Dictionary Online也有一例

In this school, most of the children are from the Chinese community

but most of the amercian still dosen't know who i am 冇錯

吹毛求庛d可以話係, but most of the amercian still dosen't know whom i am

I believe so　＝　我相信是這樣
the world is going mad = 個世界快會顛

But most of the American still did not know who I am.
I had never heard of voice like that in my life.