Answer:
B. quadratic
Explanation:
The numbers of dots are 1, 5, 12, 22, 35.
These values do not have a common ratio, so the sequence is not exponential.
First differences are 4, 7, 10, 13. These values are not constant, so the sequence is not linear.
The differences are not decreasing, so the sequence is not logarithmic.
Second differences are 3, 3, 3. These values are constant, so the sequence is described by a 2nd-degree polynomial. The pattern is quadratic.
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The pattern can be described by ...
f(x) = (3x -1)x/2