Question

why were most northerners opposed to the annexation of texas?
they did not believe the united states should expand beyond its current borders.
they believed that texas would draw their labor force away from the north.
they did not want another slaveholding state admitted to the union.
they were concerned that texas would become an industrial rival.

Explanation:

During the time of the proposed annexation of Texas, the North - South divide over slavery was a major issue. Texas was a slave - holding region. Northerners, many of whom were opposed to the expansion of slavery, did not want another slave - holding state admitted to the Union as it would shift the political balance in favor of the slave - holding states in Congress.

Answer:

They did not want another slaveholding state admitted to the Union.