Which phrase is the best definition of culprit

Which revision, if any, best fixes the bolded (capitalized in this case) part of the sentence? female cardinals, a somewhat drab bird compared to the males, blend in well with their environment. no change somewhat drab birds a somewhat drab's bird somewhat drab bird's

Walking is not the most exciting form of exercise a person can take on for fitness. yet it is low impact and requires no fancy equipment. that makes walking a simple activity for those new to exercise. walking is less likely than other exercises to cause injury to leg tendons and muscles. all it requires is a good pair of sneakers-no cables, stylish outfits, or weights required. of course, a person could increase the benefit of a workout by adding weights or speed walking. identify the main idea of this paragraph. walking is a difficult and safe exercise for beginners. walking is an easy and safe exercise for beginners. walking is a boring and dangerous form of exercise. walking is an exciting and very effective form of exercise.

Someone get back to me , i really don’t get this