Final answer:
Control of property is the insurance policy condition that allows William to collect for the loss when Brent accidentally smashes the window display while dancing. This provision applies because Brent, the employee, had control over the property during the incident, even though he is not the named insured.
Step-by-step explanation:
The condition that allows William to collect for the loss on his insurance contract due to Brent's accident is Control of property. This condition is concerned with the actions of persons who have control of the insured property and not the named insured directly. Since Brent, an employee, was acting within the scope of his employment and had control over the property at the time of the accident, this condition would apply. Therefore, William can file a claim with his insurance company under the 'Control of property' provision, assuming all other terms of the policy are met.