If the universe was born at the big bang, what existed before then?

space-time

Explanation:

The initial singularity is a gravitational singularity predicted by general relativity to have existed before the Big Bang and thought to have contained all the mass and space-time of the Universe.

The statement that best describes the main reason Southerners supported the annexation of Texas would be that "(D) They wanted more territory and land where slavery had been established," since this was during the era when the issue of slavery was decided by "popular sovereignty" in each new state.