5、Would you address character description for the commercial and industrial arts staff?
翻译为：你能够给商业与工艺美术的职员讲讲特征描述吗?
arts跟前面的commercial and indutrial连在一起看，而非与后面的staff:(the commercial and industrial arts) staff.
6、There are a number of other positions to consider.
"A number of" 换成 "a lot of" 或者是"a great many"行不行，为什么?
可以换成a lot of或a great many of,因为position是可数名词。如果这里是不可数名词，则只能用a number of代替而不能用a great many.修饰可数/不可数都行：a number of/a lot of,只能修饰可数：a great many of(与many性质一样)
7、Would you mind letting me take a look in your briefcase?
将"letting me"换成 "let me" 行不行，为什么?
不行，mind是动词，后面不能直接跟动词原形，一般接名词(或动名词),这里的letting是let的动名词形式。