Why is Afganistan called as the graveyard of empires despite the fact that Afganistan was ruled by various Indian and Persian Empire for centuries?​

Why were presidents andrew jackson and martin van buren unwilling to annex texas? a. they did not want texas to be admitted to the union as a slave state. b. they feared that the annexation of texas as a slave state would lead to political problems within the union. c. they thought that texas was too large to be admitted to the union as one state. d. they did not believe in the idea of manifest destiny.