Which choice completes the text so that it conforms to the convention…

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The Kaiparowits Formation is a fossil-rich layer of sedimentary rock in the Grand Staircase, a colossal sequence of rock layers stretching from Utah's Bryce Canyon to Arizona's Grand Canyon. The sandstones and mudstones of the Kaiparowits Formation were deposited ______ the Late Cretaceous, preserving many species from that time.

Which choice completes the text so that it conforms to the conventions of Standard English?

during;

during:

during

during,