Why Did the Annexation of Texas Take Place During Neither

Why did the annexation of Texas take place during neither Andrew Jackson's nor Martin van Buren's presidency?

A) The Lone Star Republic voted overwhelmingly against annexation by the United States.
B) Annexing Texas as a slave state would cause conflict between northern and southern Democrats.
C) Annexing Texas would improve relations between the United States and Mexico, thereby weakening American relations with Spain.
D) Jackson and van Buren were too focused on other more pressing issues, such as repealing the Independent Treasury Act.
E) The Lone Star Republic had expanded to the Pacific during this time and was invested in building its own infrastructure there.