Question

Between 1845 and 1848 the United States annexed Texas and

Answer 1

between 1845 and 1848 the united states annexed both Texas and California

Answer 2

In 1848 the US annexed the "Mexican Cession" - land that previously belonged to Mexico - this is the correct answer.

This land included the following modern US States:
California
Nevada
Utah
most of Arizona
part of New Mexico
part of of Colorado
part of Wyoming.