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Verbal·Standard English Conventions·Boundaries
easy
Dmitri Mendeleev’s periodic table arranged the known chemical elements by atomic weight and grouped them by recurring properties, leaving gaps for elements that had yet to be discovered. The table was first published in        its publication, chemists had no reliable system for predicting the properties of elements that had not yet been isolated.
Which choice completes the text so that it conforms to the conventions of Standard English?
A
1869, transforming the study of chemistry, before
B
1869. Transforming the study of chemistry before
C
1869, transforming the study of chemistry. Before
D
1869, transforming the study of chemistry before