题目

     Flying squirrels are a family of 44 species of squirrels．The term flying is somewhat of an incorrect name．      Flying squirrels are not capable of powered flight like birds or bats; instead, they glide （=move smoothly and quietly） between trees．They are capable of obtaining lift within the course of these flights, with flights recorded to 90 meters （295 ft）．The direction and speed of the animal in midair is varied by changing the positions of its two arms and legs, largely controlled by small soft wrist bones． This changes the tightness of the paganism对代数式4a2作合理的解释是______．