6. Insert prepositions where necessary (on, with, by, of, at, in): 1) The language is a tool ___ trade in many professional domains aimed dealing people.
2) Success the sale goods and services depends effective advertising.
3) Public service advertising supplies information that helps the public ___ some way.
4) Can you explain your stand ___ the issue you focus ___?
5) Success in career is shown increased position and income.