What does it mean to change the atmosphere of a story

Which statement describes the central idea of the text in the story learning about the holocaust

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.

What is the correct definition of a canal? a) a machine that picks cotton faster b) a large entity that can carry heavy loads c) a man made ditch filled with water d) a boat that can travel up the current