Answer: Because the acre is a measure of area, it has no definite perimeter. For example, using the examples in question one, the perimeter of the long, skinny sidewalk acre would be 17,434 feet (more than 3 miles), but the perimeter of the square acre would be 835 feet.
No other molecular fluoride of krypton has been isolated, so all krypton compounds are derived from KrF 2, where Kr is in the +2 oxidation state. Krypton difluoride is a powerful oxidative fluorinating agent. (Its oxidizing power means that it extracts electrons from other substances and confers on them a positive charge.
Kryptonite is the name given to shards of matter cast off from the planet Krypton after its destruction. In the Pre-Crisis Continuity depending on the particular dimension such as Earth-One, there were many forms and shades of Kryptonite, while others showed only one form such as Earth-Two and Earth-Three.