(A) 2-Bromobutane on reaction with sodium ethoxide in ethanol gives 1-butene as a major product
 (R) 1-Butene is more stable than 2-butene

2-Bromobutane on reaction with sodium ethoxide in ethanol gives 2-butene as a major product. The alkene formed in greatest amount is the one that corresponds to removal of the hydrogen from the β-carbon having the fewest hydrogen substituents. As the more substituted alkene will be the more stable, and therefore the more favored.