TOEFL Listening: TPO-TOEFL阅读TPO - NG2J2Y5XBKG6D_VAN$

According to paragraph 1, what pattern did scientists notice when the known elements were written in order of increasing atomic mass? A. The elements of the group of alkali metals were the first elements in the order of increasing atomic mass. B. Repetition of the same atomic masses for elements in different groups appeared. C. Elements with similar chemical properties appeared in the listing at regular intervals. D. Elements were chemically most similar to those just before and after them in the order.