(32)                

A In short, libraries have not contributed much to the extension of knowledge, so they have become almost indispensable to all literate men.

B In short, libraries have contributed so little to the extension of knowledge that they have become almost indispensable to all literate men.

C In short, libraries have contributed so much to the limit of knowledge that they have become rarely indispensable to all literate men.

D In short, libraries have contributed so much to the extension of knowledge that they have become almost indispensable to all literate men.