Scientists measured the density of goblet cells in the lungs and the density of mucus in the lungs for three groups of people: • people who do not smoke and do not have lung disease • people who smoke tobacco but do not have lung disease • people who smoke tobacco and have lung disease. The findings are given in the table. What do these data suggest?
- A1, 2 and 3
- B1 and 2 only
- C1 and 3 only
- D2 and 3 only