Question

此句成分分析及具体翻译谢谢！详细点！

It suddenly dawned on me that this express was not roaring down the line at ninety miles an hour, but barely chugging along at thirty.

Answer 1

it 做形式主语，but 后面的句子是对that从句的伴随状语。
译：我突然明白,这列快车并非以每小时九十英里的速度行驶,而是以每小时三十英里的速度缓慢地前行。

Answer 2

先说主谓宾：
主语是it 做了形式主语，真正的主语是that后面的全部句子，为了避免头重脚轻所以用了it，谓语是dawned on
宾语是me
从句分析
chugging是与roaring down并列的然后用了副词barely修饰chugging.

Answer 3

真辛苦啊，要老师的同学