Answer:
The Republic of Texas was sparsely populated, the Native American population was hostile to white settlers, and the white settlers themselves were hostile too, leading to social conflict.
Besides, the Republic enjoyed very little international recognition, had Mexico declare war on it, and most of the population wanted to merge with the United States.
These factors ultimately led to disappearance of the Republic and its merging with the United States.
B and D don’t make sense logically, so i would probably choose A. C could work but i think A is your best bet. sorry i couldn’t be more specific!
The Consitution was the reason why Jefferson hesitated to purchase the Louisiana Territory from France. This is because it did not have anything about buying land and the rights to the President in it.