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.
Years ago, Krypton was about to explode and Kal-El was sent to Earth to escape that fate. However, his older cousin, Kara, was also intended to accompany the infant as his protector. Unfortunately, Kara was accidentally diverted into the timeless Phantom Zone for years before finally arriving on Earth decades later and found by her cousin who had grown into Superman.