Critical Reasoning

Among the most effective kinds of publicity that publishers can get for a new book is to have excerpts of it published in a high-circulation magazine soon before the book is published. The benefits of such excerption include not only a sure increase in sales but also a fee paid by the magazine to the book’s publisher. Which of the following conclusion is best supported by the information above?

1) The no .of people for whom seeing an excerpt of a book in a magazine provides an adequate substitute for reading the whole book is smaller than the no. for whom the excerpt simulates a desire to read the book.
2) The effectiveness of having excerpts of a book published in a magazine, measured in terms of increase in sales of a book is proportional to the circulation of the magazine in which excerpts are available.
3) Books that are suitable for excerption in high circulation magazines sell more copies of books than are those not suitable for excerption.

Hi I can rule out option 1 because the people whose desire increased after reading the excerpt mayn't directly buy the book!!

How o disitnguidh between optins 3 and 4?