A healthy amount of exercise helps to maintain a healthy respiratory system. Therefore, the answer is D. reading a book
you can also use test taking skills when answering this question by concluding that reading a book is most different from the other choices that involve exercise.
The correct answer is (a.) coma. Vaporized gasses and released dust that forms a bright cloud called a coma, around the solid part of a comet. Coma is in a nebulous envelope form that surrounds the nuclei of a comet.
