Florists, personal trainers, and chefs all have healthy jobs according to research. There are many reasons for this. A florist, for example, sells flowers and plants to customers. A personal trainer, on the other hand, is usually very fit. He or she trains other people to lose weight and to keep fit. These jobs are relaxing because they may not cause much stress.

However, research also shows that some jobs are "unhealthy". They cause a lot of stress and worry. For example, a taxi driver drives all day. He often faces traffic jams and difficult passengers too. A firefighter puts out dangerous fires and sometimes saves people from burning buildings.

Most people are looking for the perfect job. They want a job that is interesting, with a good salary and not much stress. However, to get everything is really difficult. Healthy, relaxing jobs are usually not very well paid. On the other hand, people with stressful jobs often get good salaries. For example, the head of a big company gets a lot of money, but he or she does not always have good health, or the time to enjoy life.

The word "They" in paragraph 3 refers to __________.