On February 25, 200–300 Mexican soldiers crossed the San Antonio River and took cover in abandoned shacks approximately 90 to 100 yards (82 to 91 m) from the Alamo walls. The soldiers intended to use the huts as cover to establish another artillery position, although many Texians assumed that they actually were launching an assault on the fort. Several men volunteered to burn the huts.To provide cover, the Alamo cannons fired grapeshot at the Mexican soldiers, and Crockett and his men fired rifles
 
        
             
        
        
        
Russia has been a notoriously difficult country to invade, given its large size and generally large population throughout history. Freezing winters have also played a role in helping protect Russia, which was famously noted in 1812 during Napoleon's failed invasion of Russia. In response to European nations who saw the new French government as threat to the balance of powers, Napoleon annexed various parts of Europe and launched an invasion of Russia with over 600,000 soldiers. Napoleon invaded in the summer of 1812, but long fighting and a scorched earth policy by Russian forces prolonged the fighting and when a harsh winter arrived, the French army that lacked in supplies was reduced to under 100,000 soldiers. Eventually, Napoleon conceded his defeat, and left Russia in December, 1812.
        
             
        
        
        
Answer:
I believe the answer is either C or D.  But more likely is C!
Explanation:
I think it is not A because the British were actually having a hard time "preventing" the mass flood of people going west.
I don't think it is B because it would not be possible to enforce them.
It would be possible to be D but the British had the problem of the Native Americans who were killing the settlers. So the British had to focus on treaties and such. 
I think it is C because the British had to try to prevent the mass floods going west. They were overrunning and destroying treaties made by the British. I think it was called the "Proclamation of 1763" in which banned/restricted/limited the amount of Settlers to pass the Appalachian Mountains. 
Although honestly, probably the main problem the British faced was the debt they were in after the way in which you will see the end result in the American Revolution. But that isn't a choice on here.