Answer:
a. Schools operate for the full year, so no students are looking for summer work.
This will cause that the total labor force decreases, so the natural rate of unemployment will decrease. The natural rate of unemployment includes only structural and frictional unemployment. Since no students will look for summer jobs, then frictional unemployment will decrease, therefore, total natural unemployment will decrease also.
b. The Internet lists all the jobs available in the whole country, so it is easier for job seekers to locate potential jobs.
This will help to decrease structural unemployment which will in turn decrease the natural rate of unemployment. Structural unemployment happens when an unemployed individual cannot find a job that fits his/her skills. Internet job postings will make it easier for unemployed people to find jobs that match their skills.
c. People who quit their jobs are drafted into low-wage community-service jobs.
This should reduce frictional unemployment (which reduces the natural rate of unemployment), since frictional unemployment is made up of people that quit their jobs in order to search a better job or are looking for their first job ever. If people realize that quitting their current jobs will result in them being drafted into low wage jobs, less people will quit their jobs. This doesn't mean that they will stop searching for a better, it means that they will continue searching for a better while still employed.
d. In addition to unemployment insurance, the unemployed receive a bonus for finding new jobs; the bonus is greater if the job is found in the first few weeks of search and declines with the duration of search.
This should motivate people to get any available job as quick as possible. Sometimes a person that is fired will not accept possible jobs because they consider that they can get a better job, so they decide to wait until they get the job that they want. If a bonus is given, a lot of people will be motivated to accept any new job that they can find as long as it allows them to collect the bonus. This doesn't mean that they will quit looking for their dram job or the job that they deserve, it means that they will be working while doing so. This should decrease the natural rate of unemployment.