The british policy of salutary neglect:
a. prevented the colonies from developing diverse economies
b. sent many royal officers to run the colonies
c. enforced strict laws such as the navigation act
d. allowed the colonies economic freedom

The best answer is, it allowed the colonies economic freedom 

Siege of Yorktown, also known as the Battle of Yorktown, the Surrender at Yorktown, German Battle or the Siege of Little York,[a][b] ending on October 19, 1781, at Yorktown, Virginia, was a decisive victory by a combined force of American Continental Army troops led by General George Washington and French Army troops led by the Comte de Rochambeau over a British Army commanded by British peer and Lieutenant General Charles Cornwallis. The culmination of the Yorktown campaign, the siege proved to be the last major land battle of the American Revolutionary War in the North American theater, as the surrender by Cornwallis, and the capture of both him and his army, prompted the British government to negotiate an end to the conflict. The battle boosted faltering American morale and revived French enthusiasm for the war, as well as undermining popular support for the conflict in Great Britain.

Answer is after the battle at Yorktown When did the British surrender