Why is Answer E correct?

The second sentence says "Through the fourth century B.C., Mesopotamian cities engaged in trade, but had never had marketplaces" but can the correct answer choice be this simple? And more broadly, do all questions have written explanations for right/wrong solutions? Thank you so much!

Hi Edwin, We are told that MS happens only with MKP, so If MS -> MKP and If not MKP -> not MS And that the Mesopotamians did not have a marketplace, so therefore, they must not have had a monetary system.