Comprehension Passage
Study the following table carefully to answer following questions. The table represents the number of workers employed in four units of a company over the years.
| A | B | C | D | |
| 2000 | 205 | 170 | 150 | 190 |
| 2001 | 106 | 120 | 200 | 170 |
| 2002 | 190 | 180 | 210 | 104 |
| 2003 | 130 | 178 | 205 | 190 |
| 2004 | 140 | 152 | 160 | 160 |
| 2005 | 132 | 145 | 180 | 155 |
For all given years what is the difference between the average number of workers in units B and D?
1
3.5
2
3
3
4
4
4.5