Which of the sentences below best expresses the essential information in the highlighted sentence in the passage? Incorrect choices change the meaning in important ways or leave out essential information. A. Some characteristics of masks must be due to cultural and national factors, such as whether they were made during a period of warfare or of peace and trade. B. As one contiguous nation exchanged masks with another during trade or warfare, it became more difficult to determine he place of origin of masks. C. Some differences among masks were probably due to their different origins, but because they passed from one nation to another, their origin cannot always be determined. D. As masks of different cultural origins passed from one nation to anther during trade or warfare, they acquired certain differences depending on how they were used.