請問TPO7 閱讀 Mediterranean那篇的插入題

redable

Paragraph 2 ■Another task for the Glomar Challenger’s scientists was to try to determine the origin of the domelike masses buried deep beneath the Mediterranean seafloor. ■These structures had been detected years earlier by echo-sounding instruments, but they had never been penetrated in the course of drilling. ■Were they salt domes such as are common along the United States Gulf Coast, and if so, why should there have been so much solid crystalline salt beneath the floor of the Mediterranean? ■
12. Look at the four squares ■ that indicate where the following sentence could be added to the passage.

Thus, scientists had information about the shape of the domes but not about their chemical composition and origin.

我選D,因為有Thus,我判斷是最後一句，但答案是C 但上一句要怎判斷跟shape有關呢
謝謝~

pingming

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