Standard English Conventions — module quiz

Bathymetric charts of the mid-century Atlantic were assembled from thousands of individual soundings, each one a single depth reading taken from a ship. In the early 1950s the geologist Marie Tharp plotted those readings into a continuous profile of the North Atlantic floor ______ and identified in it the deep rift valley that would become central evidence for seafloor spreading.

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