一、原题按正常成分顺序可整理如下：
The students were surprised to see him,a stranger,enter the classroom carrying a bowling ball.
这样就可以作如下的粗略语法分析——
* 主语：The students
* 复合谓语动词：were surprised to see
* 重叠复合宾语（宾语+不定式宾补+分词宾补）：
1、him,a stranger,enter the classroom
不定式在知觉动词后作宾补,表示动作由始到终的全过程,即“看到他,一个陌生人,走了进来”
2、(him,a stranger,) carrying a bowling ball.,
现在分词在知觉动词后作宾补,表示感知到的是一个正在发生的动作,看到（他,一个陌生人,）正拿着一个保龄球.
由此可见,原题的 a stranger 是宾语 him 的同位语,由于强调被提前到句首,意思是“有一个陌生人,学生们吃惊地看到了他…”.
二、the students were surprised to see a stranger carrying a bowling ball enter the classroom 中,各部分的语法成分保持不变,所变动只有两点——
1、用原同位语 a stranger 取代了宾语 him
2、宾语补足语的顺序做了调整,把原来的意思“看到他进了教室还拿着保龄球”,调整为“看到他正拿着保龄球进了教室”
因此,这个句子与原题的意思相同.
三、A stranger carrying a bowling ball,the students were surprised to see him entering the classroom.中有两处不妥——
1、A stranger carrying a bowling ball 和 the students were surprised to see …
尽管没有改变原题的意思,但却是两个没有任何连接手段的句子,应该在中间添加 and 或者把逗号改为分号.
2、 to see him entering the classroom
原题的不定式 to see him enter the classroom 变成了现在分词,把原来的“看到他进了教室”变成了“看到他正走进教室”,前者表示已经进去了,后者则表示还没有进去.
因此,这个句子改变了原题的意思.
再问： 那这个the students were surprised to see a stranger carrying a bowling ball enter the classroom 是不是see a stranger enter the classroom是主干然后carrying作伴随啊？
再答： the students were surprised to see a stranger carrying a bowling ball enter the classroom 意思相当于 the students were surprised to see a stranger carrying a bowling ball (and to see him) enter the classroom，语法上把这种前后两个相近的结构称作重叠成分（此处是重叠宾补），相当于并列成分。
