What clause requires that the homeowner have insurance equal to 80% of the home's replacement value?

The correct choice is the coinsurance clause. This clause is commonly found in property insurance policies and requires the homeowner to carry insurance equal to a specific percentage—typically 80%—of the home's replacement cost. The purpose of this requirement is to ensure that the property is adequately insured to cover potential losses.

In the event of a claim, if the homeowner does not maintain insurance at the specified level, they may receive a reduced settlement. This clause encourages policyholders to insure their property for its full value to prevent underinsurance, which could lead to out-of-pocket expenses in the case of a loss.

The other options do not fulfill the same function. A liability clause pertains to coverage for bodily injury or property damage to third parties, while a property valuation clause may relate to how the property's value is determined but does not specifically mandate a percentage of coverage. A replacement cost clause generally refers to how claims are settled (i.e., replacing damaged property with new property of similar kind and quality) but does not impose an insurance requirement like the coinsurance clause does.