In general, bat proofing of buildings involves sealing of any openings greater than:

The correct answer is based on the size of openings that bats can use to enter buildings. Bats are known to be able to squeeze through very small gaps, and research indicates that openings greater than 1/4 inch can allow bats access to a structure. Therefore, to effectively bat proof a building, any openings equal to or larger than 1/4 inch should be sealed to prevent bats from entering and roosting inside.

This sealing process is crucial, as it helps to mitigate any potential health risks associated with bat droppings and keeps the integrity of the building intact. Closing off larger openings, such as those mentioned in the other options, would be helpful, but the focus is on the maximum size that would necessitate sealing for effective exclusion. Thus, paying attention to openings greater than 1/4 inch is the standard practice in bat proofing structures.