Count the dots in each box and compare each count with the one before it. How many dots will the next box have?

The counts are 1, 2, 4, 7. The increases are 1, 2, 3, so each increase is one more than the last. The next increase is 4, giving $7+4=11$ dots: (b). (a) repeats the last increase of 3, (c) adds 5 and (d) adds only 1.