Why did cos surrender at San Antonio?

As tensions between Mexico City and Mexican Texas increased, Cos headed north to put down the rebellion. After a 56-day siege of the town and the Alamo Mission, on December 9, Cos surrendered San Antonio de Béxar and its weapons to the Texians, then proceeded to retreat back across the Rio Grande.

Answer C. Rapid increases in southern cotton exports

The South was affected by the Civil War in many ways. One way was that slavery and all that slavery represented came to an end. ... As a result, the South had to be rebuilt after the Civil War ended. This led to a diversification of the southern economy as more industries were built in the South.