The correct option is C. It shows a positive effect of the solution.
The topic of the presentation is the impact of excessive homework on highschool. The word "excessive" implies that the amount of homework given at highschool has a negative effect on students. The solution would be to have "less homework" and she finds out a positive effect of such a solution. If students are given less homework, they will have time to do other enriching activities and spend time bonding with their loved ones.
The troposphere is the lowest level of the atmosphere, so it is in contact with the Earth's surface. In contrast, the stratosphere is located above the troposphere, so it is not in contact with the Earth's surface. ... The air density and air pressure are much lower in the stratosphere.
