The following 20 numbers represent the number of pages read by a student each evening over a month:
2, 4, 2, 5, 6, 4, 2, 7, 4, 5, 6, 4, 2, 5, 4, 6, 2, 5, 6, 4.
Which option correctly states the mode and its frequency?
a) 2 pages, read 5 times
b) 4 pages, read 6 times
c) There is no mode
d) 4 pages, read 5 times