In this figure sequence, there are four different shapes labeled I, II, III, and IV. Each shape has a number of sides ranging from 2 to 4.

If we observe the pattern, we can see that each new shape is adding one more side than the previous shape.

In option I, the shape has 2 sides. This does not follow the pattern of adding one more side with each new shape.

In option II, the shape has 5 sides. This also does not follow the pattern.

In option III, the shape has 6 sides. This fits the pattern as it adds one more side than the previous shape.

In option IV, the shape has 7 sides. This does not follow the pattern as it adds more than one side compared to the previous shape.

Therefore, the correct answer is option III.