A sales manager has sampled past sales records to determine how many refrigerators are sold each day. Daily records for a sample of 10 days have been selected. The sales on these days are: 0, 4, 4, 2, 1, 3, 4, 5, 2, 7. The mode of data set is ______.

Select one:

a.

3.5

b.

3

c.

4

d.

2